Revert "book 4"

This reverts commit 45ca1971ebf47c3819a50b3daedae55471d58958.
Revert "book 8"

This reverts commit b50800dcfb9f8be15723d23b95adbf305422031f.
Revert "book 9"

This reverts commit 366ec7e1b25edcc2a1f369e1ac3c5927b99d500b.
book 9
Revert "book 10"

This reverts commit 360144719902c1eb31512f5e641a939481824343.