The odyssey is not designed for the DAT. Its more for students who struggle with Orgo class.
The Odyssey it not an "orgo text book", its just a bunch of questions (multiple choice) and answers. Thats it.
the questions are FAR more difficult than anything you'll have on the DAT, so its, in my opinion, a waste of money. I bought it back in 2007 right before I took Orgo 1 because I was always told that "OMG ORGO WAS THE HARDEST UNDERGRAD COURSE I EVER TOOK"... I was scared outta my mind and I thought I was going to bomb orgo, so I wanted to be as prepared as possible. Turned out, Orgo was fairly an easy course, and I never used the Odyssey, right now its sitting on my bookshelf collecting dust