I am using the book class for my thesis. However, the default alignment is very strange as shown in the following sample.

As it shows, extra space was added between lines so that the content is filled over the whole page. What I need is to fill the page normally wihout the extra space?
use this
– Cristian Rodríguez Dec 21 '14 at 03:09\raggedbottomcan eliminate the extra vertical stretch, but of course that means that the page won't be full. – Steven B. Segletes Dec 21 '14 at 03:10amsmath, there are tactics to allow page breaks under your control; consult the users guide:texdoc amsmath. – barbara beeton Dec 21 '14 at 15:55