Yes, just start from the beginning again, read a few pages and do some coding examples to verify that you understand everything. The coding part is very important to grasp the concepts and to deepen your knowledge. Don't give up, you will get it as long as you give yourself time to understand it. Some people read the book three times and still learn things the third time!
I agree with Frits - every few pages you should stop and actually code the examples or concepts that you just read about. Nothing like writing code, compiling and seeing the resulting web app in action to cement what you've read in your memory. You can't learn software development without actually doing it.