It would not help the rankings of your main website booksforsale.com because your redirected domains would not be authoritive with a 301 alone. You would need relevant, quality back links to those redirected domains to build up back links. The problem then lies with the 301 redirects. 301's do not pass 100% of link juice. So while you can be building links to your main domain and getting 100% of the link juice you're really hindering your own efforts.
The websites such as sci-fi-books.com would help if there were very very few websites which contained those keywords on the internet which is not likely. The keywords in the domain name alone would rank if they were extremely unique. But since that's not likely and Google is taking into considering hundreds of other signals a newly registered domain redirecting to your primary domain isn't going to help much.
You should maybe build up genuine content on these domains and link to your primary rather than doing a 301 redirect. It sounds like you are trying to hurry the process of ranking naturally and this is really cutting a lot of corners. It's not worth the time or money.