Besides the official book which has one mock test, are there any mock test books/resources that have tests with the proper difficulty level?  I noticed in the comments of a mock test book series on Amazon Japan that most of the test books are easier than the actual test except for the official book.

I used the N2 version of this book for studying and it was great. It has lots of questions for each question type, more than a typical mock test has. It also has one or two full mock tests in the back if I recall (not 100% on this). I imagine the N1 version would be just as useful for practice.
http://www.amazon.co.jp/dp/4757418779

I use the ゼッタイ合格！ mock test books. They aren't easy (they're more difficult than the quizzes in my prep books), but I've only taken the JLPT once, so I can't really compare them that well. You get three of them in one book though, and they're pretty cheap; between those and the official mock test, you should be set.

In my opinion, the main difficulty of the JLPT is the time limit on the first half; mock tests help by getting you used to the format and preparing you for what the test is like, the rest of it is just having the knowledge and reading speed required to pull out the right answers quickly.

Thanks for the book suggestions. I'll pick them up. At some point, I need to get my timing down, so like you said, mock tests are the way to go.

I've used both the ゼッタイ合格 and another set of N1 mock tests from a different publisher; they both seemed about the same difficulty level to me, which I took as an indication they probably weren't too far from the real test difficulty.

I ordered the two books mentioned here from Amazon Japan. I should get them in a few days. I'll let you know what I think after I receive them.