I'm wondering what the reason is for so many of his classic books to not be on there. when I ordered my kindle, he was one of the authors I was planning on loading up on. but most of my favorite books of his are not available yet
I suspect that the reason Crichton's earlier works are not available in ebook format is that they were published before computer-based typesetting became common. The publishers don't have any existing digital files to work with. In order to publish an ebook version of Jurassic Park, they'd have to scan the pages and have an editor go through the entire text to correct OCR errors -- or have someone retype the entire book from scratch. Crichton frequently includes illustrations in his books, so those would have to be digitized and cleaned up. Then they have to put in all the formatting codes so that the book displays correctly on different devices (Kindles, Nooks, etc.).
Publishers have huge backlists of pre-digital books that people are clamoring for and it's very labor-intensive and expensive to convert them. I'm sure it will happen eventually given Crichton's popularity, but they can't just pop out a Kindle version whenever they feel like it.