Most people seem to use Barrons and Dr. Chung’s along with the 3 available real tests. I have been looking over Mad Math Database, with problems sorted by category. Some of them are a little repetitious, it seems pretty useful, and fairly difficult material. I also liked Dr. Jang’s Math SAT Level 2 800. It is mostly material on each type of problem, with several tests at the end. The material seemed difficult, but fairly realistic, so I thought it might also be useful for a student seeking a top score. I would be interested in other opinions on these or other materials.
Been going through the Jang book, which came out this year. I tutor the test and get at most 2 wrong on a realistic test. Many of the questions in that book are difficult for me. It is useful for me. I think it would be useful for a student close to 800.