These are two extremely powerful social media companies that have enormous audiences and can be used to help promote books, but they vary wildly in their results, user experience, and the quality of the services they offer.
This was one of the first major social media sites, and in many cases it is considered to be the social media website of the world. Sure, in certain areas and demographics twitter (or other alternatives) win out, but as far as sheer scale, Facebook is hard to beat.
Facebook does a lot of algorithmic tweaking to determine what to show, how to show it, and the types of articles people like to see. The problem with this is that often content that is important can be suppressed simply because Facebook is trying to maximize engagement.
Hence, cat photos can perform better on facebook than articles that actually mean something to the value of the world simply because they are more likely to get 'likes'.
This, for authors, is good and bad. It means that creating unique and highly engaging content that a lot of people click on will be rewarded, but it also means that it is easy for your content to get suppressed from timelines with the intention that outreach must be paid for.
Style of Advertising
Cost per click, but they have added in some easy boosting options to really try and help people out who aren't experienced but want to promote their content. For instance, there is a 'boost' button on all posts (on a facebook page) so that you can spend money to reach a targeted audience and get more impressions for your content. The boost used to be very weak and ineffective, but recently they've made it smarter and have more advanced targeting so it isn't a terrible way of entering the 'advertising game' as simply as possible.
They vary up the styles of their campaign across goals, like getting people to view your content, or driving engagement or website clicks. You can even integrate fully with a website for tracking sales to determine exactly how much you are earning from the ads, but those are usually outside the reach of normal advertisers.
For authors, what it means is that you can pretty quickly get an ad up and running to target specific audiences around the world and hopefully drive new readers to your books.
The one nice thing about facebook is that engagement is relatively high, and if you manage to drive clicks on their website then those clicks might easily be translated into sales. This is why their advertising can be expensive, and organically people respond fairly well to posts.
Outreach without Ads
The thing about the ads is that they are completely necessary now.
It used to be that if you had a page for your brand and people liked it, then when you posted content they would see it. Or, around 60-90% would have it added to their feeds and updated to them organically.
Now, that number is closer to 10-30% of your fans who will see your regular content. Facebook is simply thinning out the content and choosing what to show to keep the feeds relatively free of advertising, and the only way around this is to pay for advertising.
If you boost your post, you could easily push that number back up to 90% and beyond into new readership, but a lot of people are angry that facebook has made it more difficult to get content in front of users.
I can understand things from both perspectives: people don't like to be spammed with useless advertisements, so facebook is making their system pay-to-play. But, it just raises the cost of entry for people and makes it harder to use.
Price of Ads
The cost per click varies wildly depending on the type of engagement you are shooting for as well as the time of year/week you are running the ads. I've had them run as little as 5-10 cents per click all the way up to 1.50 per click. It doesn't take very long before the cost is too high to have any value, however, it is important to monitor the cost constantly to make sure you aren't throwing money away.
Running a facebook page is relatively easy, and running the ads is even easier, but if you plan to invest in facebook you truly will need to open up the checkbook and invest.
That being said, with a highly targeted ad and a little experience, you can easily generate a decent ROI and at least make your money back.
However, if you aren't experienced with CPC ads or don't want to spend the time working with it, I would recommend using the boost system and deciding exactly how much you want to spend. It is easy to set a high daily value, forget about it, and wrack up hundreds of dollars in costs with very little to show for it.
Twitter is one of the easiest places to deliver and consume succinct content. They designed their entire system around posting limited characters, and that has been their saving grace.
They are also a strong network with the use of hashtags and trending lists to understand what the nation is engaging with.
Unlike facebook, twitter was notorious for not including algorithmic filters into their system. Anyone could post anything, and the most popular content filtered to the type by simple virtue of numbers. What this meant for the overall system was that national conversations could take place on twitter and it was a quick way to blast out momentary thoughts to the world.
However, in recent times twitter has begun shifting in the other direction and trying to find new ways to display their content. They are limiting feeds and assigning value to posts, which means they are gradually transitioning to a system closer to facebook.
This is, in general, good for authors because it makes writing engaging and value content to be a rewarding effort more than it was previously.
Style of Advertising
They also have CPC advertising, as well as a few other systems. Similar to facebook, their pricing structure is all over the place, but in general I've managed to run fairly cheap ads. However, if you don't specifically set a price point cheap, you could easily overspend on twitter and get very little in return.
Outreach without Ads
Tweeting is like screaming into the void. Everyone is screaming at the top of their lungs and just hoping they can be louder than everyone else. The thing is, twitter is the easiest place to retweet and share, so it goes through content so much faster than any other platform it can be difficult to keep up with.
Getting your voice above the crowd is difficult, and even when you do there is very little in regards to a receptive audience that wants to hear your opinions or buy your book.
This means that when you see websites saying they have hundreds of thousands of followers, it is the same thing as other websites having twenty to thirty thousand, because those followers are likely to be more engaged than these followers.
That being said, building a twitter following is valuable, and it is a good platform for readers to get to know you and learn more about you as a content creator.
Price of Ads
Twitter is certainly cheaper than facebook, but only in the case that you are very specific with targeting and setting a price point. In general, however, those clicks result in less return on investment because people don't often follow through and buy the content.
I occasionally run ads on this platform, but in general I would recommend steering clear or setting very low bid advertisements and being patient regarding the results. It simply doesn't have the same return on investment that facebook can generate.
That being said, people have had tremendous success through this platform, so it is worth testing out for yourself and determining viability.
Which is better?
For outreach, twitter is the easiest platform to use, but facebook generally has a better response. The only problem is, facebook also curates content, which means they expect for authors to pay to have their content viewed.
I would recommend trying both, but when you run ads be very careful to limit them to run slowly so you can monitor them closely and see which has a better return for you. If you are new to advertising, I would start with facebook, because their platform is a little bit friendlier to newcomers.