I use goodreads to search / log all my books. Not much experience with promotional pages but things I look for (non fiction):

• Who's the author?
• What's it about? Does it cover what I'm looking for? No need for free sample but maybe table of contents or list of topic it covers.
• Might do some research -> is this a classic book on the topic?
• Ratings, but I don't care too much about them

Then I'd put it on a to-read list and come back to it later.

Hope it helps!