I'm always nervous when I buy doujinshi on Yahoo.jp, because the sellers only post a picture of the cover and virtually no description (the best you get is the number of pages), so it's impossible to tell what the content will be like. Considering some of the REALLY fucked up things you can find in doujinshi (*shudder*), I'm always scared of accidentally buying shouta gang rape or something horrific like that D:
Or heck, even if the content is completely harmless, it might just be crappy. I've seen books with absolutely gorgeous cover art and disappointingly fugly inside art.
But I've been lucky in the past. Limited edition fan-made book with gorgeous art of your favourite characters telling a story about your OTP? Hell yes!
So, even if the risk of getting a book I might have to burn is ever-present, I've decided to buy another batch. Fingers crossed!