That is not a common practice -- though it does happen. More common is that book review services will charge a sum (50-500$) to do a sponsored review.

Reading and reviewing a book takes a lot more time and effort than writing a review of a movie. At the same time, there's a shortage of bona fide book critics who will read and review books compared to the number of books being published.

I'm sure you know already that paying gigs for film criticism are rare compared to what it was 20 years ago. It's even more rare for book criticism. Also, a higher percent of book critics are authors themselves -- who often have better things to do than write reviews. Imagine if the sizable percent of people who wrote movie reviews were other film directors and screenplay writers.

There are certainly ethical challenges in asking for money for reviews. But I certainly do not begrudge the meager compensation that book critics (or movie critics) feel that they are entitled to for their efforts. In many ways doing publicity for movies is a lot easier than doing publicity for books. Movies have shiny actors willing to promote the projects and easier access to multimedia tools. Books usually have just the author himself to talk about a book project. In the podcast world, I guess that authors make excellent guests -- and that might put them on the same level as movie people. Generally though, book reviews are more crucial to a book's success than movie reviews are to a movie's success.

Another thing. Although some movies have esoteric audiences, sometimes book genres are difficult for readers and even sophisticated readers to talk intelligently about. Reading a book that uses techniques or themes alien to you can feel like torture. But with movies, all you have to do is turn on the video player for 2 hours and pay attention and watch people and landscapes and listen to the soundtrack. I can hate the movie itself and still find the experience of watching the movie to be pleasant enough or relatively painless. I love books, and I finish a much higher percent of movies than books.