Just finished reading this book and all the endings and I love love love this book. Wish we still had more gamebooks like this in print. The level of detail and description, and the sense of adventure is really great. Even though I never read it as a kid (I had other CYOA books that I borrowed from the library though) it still feels pretty nostalgic.
I also love that there isn't just one "good" ending (good implying that you get back to your own time). There's quite a few where you make it back to your own time, some with a dinosaur egg, some with an open-ended kind of ending.
Also, there are some where you don't get back to your own time but you nevertheless become successful in a different time. It still counts as a win in my book. I'm giving this 5/5.