The following shortcut keys can be used when in the Reader.

Function Key
Next heading ⌘ + Arrow up
Previous heading ⌘ + Arrow down
Next page ⌘ + SHIFT + Arrow right
Previous ⌘ + SHIFT + Arrow left
Go to page ⌘ + G
Next 15 seconds ⌘ + CTRL + Arrow right
Previous 15 seconds ⌘ + CTRL + Arrow left
Go to the beginning of the book ⌘ + HOME
Go to the end of the book ⌘ + END
View list of headings CTRL + H
View list of pages CTRL + P
View list of bookmarks CTRL + B
Add bookmark ⌘ + B
Remove selected bookmark ⌘ + CTRL + SHIFT + B
Edit selected bookmark ⌘ + SHIFT + B
Search in book ⌘ + F or CTRL + F