The Books are listed by 'Topic' - and the 'Topics' are listed in 'Groups'.    The left hand side Menu lists these Groups and Topics and you can use this menu to view and browse information about each book that relates to a specific Topic - by 'clicking' on the Topic name.

This side menu will continue to be displayed when you are viewing a Topic - so that you can easily look at lists of other books under similar Topics or Groups.

Note: You can see more information regarding the choice of Topics and Groups - by 'clicking' on the upper horizontal Menu choice 'Browsing Hints'