I'm finding out that writing a book is just the beginning of the job of an author.
Gone are the days when authors could submit their finished manuscript to a publisher who would then give it to an editor to make corrections and suggestions of ways to make it better.
Gone are the days when the publisher promoted your book.
We either have to pay to have our book edited or have some kind friends that agree to help. In addition to that, we need to pay to have a book cover designed.
So... self-publishing has become more popular. Since we have to do most of the work anyway, we may as well get a bigger portion of the profits. It's not easy. It takes lots of time which cuts into the time you could be writing another book. It also can take a monetary investment. Advertising is not cheap. Networking is essential.
Hence authors join reader's groups, agree to speaking engagements, and do book signings, which also need to be promoted. I say this to convey the fact that a lot of work goes into every book an author writes. True some are better than others, but if you find a good one, write a good review for them. It can help your favorite authors by promoting them to more success.
If they have success then they can write more books.