Did he leave it on purpose?

Last year I read all the books for the first time! It was the best.

I had a question about HBP though and wondered if this is something that was discussed when the books first came out. Do we think that Snape left his potions book for Harry to find? Or was this really a coincidence? It seems so unlikely that he just "forgot it was there" or this is a plot hole that was never resolved. What do you think?