Comparing your book to a best seller

Is there ever a time when it's okay to use the "If you like the 'so and so book' you've got to read 'my book'?". I personally like the reference to another book—as long as it's a book I've read or am at least familiar with. I think it gives me a good idea of what I should be able to expect from the new book that claims to be similar.

But how similar does a book need to be to make that claim? Just because it's in the same genre with a best seller doesn't mean the names should be linked. But when should they be linked? Is it the style of writing or the content that matters the most? And then you come to the next potential problem, knock off books written simply to ride on the coat tail of another book's success. Similar is one thing, I'm not looking for the same book written slightly different.

I've considered using a comparison of Left Behind for Scinegue. Not because of the writing style but because of the subject matter. Both books have very normal, imperfect characters who stumble upon a supernatural situation and have to make some life changing decisions. None of the characters have superpowers or special abilities. Both books contain a lot of very real human doubts and uncertainties. But I don't think I will make that comparison anywhere other than here on my own little blog. I think it would come across as presumptuous. Maybe once Scinegue is on some best seller lists I'll reconsider. Maybe not...