I did a little home work on this and you're absolutely right. The content is what really counts in plagiarism cases.
Since I haven't read his book, I wouldn't know if any of the content was taken from my book. I guess all I would have to do is look for paragraphs that had correct punctuation, spelling and grammar.
I dont know the anaswer to your questiona bout whether he can come up with a book with a similar title to yours but something interseting, anyone who writes a book about anything "for dummies" winds up getting sued by the people who put out the "for dummies" series. even if you are writing about a topic they havn't covered they have "for dummies" trademarked. Im a member of some webmaster and affiliate marketing forums and hear about this happening all the time.
as for similar content there's programs you can load your content into and it will tell you if someone else is using your content, thats if its on the internet so wont necessarily work on something written in print if its not on the net.
prety much everything on the interenet is copied though. many bloggers and writers use article spinning software that basically will take an article change words and whamo there's a new article