I get a lot of books for free from publishers and authors on GoodReads, probably because I do a lot of reviewing and reading. I read a lot of non-fiction, particularly art history, archaeology, and Asian studies (big surprise, huh). Something I usually do before I read the book is I look up everything I can about the author and if I don't see a strong academic and professional background that matches the subject matter - I tend not to take the book very seriously. Not that everyone needs a PhD to write seriously about a topic they love - I just think it helps quite a bit. If the introduction doesn't have a clear thesis and methodology, I almost always take off 1-2 stars. Self-published books usually get an eye-roll. Academia does need new blood, sometimes we need new ideas and new ways of looking at things...but you need to be able to back up your claims with evidence. You need to tell me how you got to that conclusion. I also need some notes and sources and it helps if you have a couple primary sources.
How big of a snot am I and how badly should I feel about writing reviews? I love to read and I don't mind writing up what I loved and hated about a book ~ but sometimes I feel mildly terrible ripping apart what somebody worked very hard on and self published.