Is it fine to say, buy Smash but post reviews on Amazon? When I get free books I post reviews asap. But didn't want to in case it'd be against Amazon or anything like that. Thanks. They're not false reviews I've read (just wanted to extra clarify lol)

Yeah, Amazon doesn’t have a problem with posting reviews there for stuff you’ve bought or read elsewhere. You just won’t get marked as a “verified buyer” on Amazon but it still helps :)