Thanks, I am currently reading the xv6-risc-book (which is also available in Chinese).
EDIT: To generate the English pdf I needed to apply pull request 35 and if you want an epub file pull request 31.
e.g.
$ cd xv6-riscv-book/
$ git config --add remote.origin.fetch "+refs/pull/*/head:refs/remotes/origin/pr/*"
From https://github.com/mit-pdos/xv6-riscv-book
* [new ref] refs/pull/10/head -> origin/pr/10
* [new ref] refs/pull/11/head -> origin/pr/11
* [new ref] refs/pull/14/head -> origin/pr/14
* [new ref] refs/pull/15/head -> origin/pr/15
* [new ref] refs/pull/16/head -> origin/pr/16
* [new ref] refs/pull/17/head -> origin/pr/17
* [new ref] refs/pull/18/head -> origin/pr/18
* [new ref] refs/pull/19/head -> origin/pr/19
* [new ref] refs/pull/20/head -> origin/pr/20
* [new ref] refs/pull/21/head -> origin/pr/21
* [new ref] refs/pull/24/head -> origin/pr/24
* [new ref] refs/pull/27/head -> origin/pr/27
* [new ref] refs/pull/28/head -> origin/pr/28
* [new ref] refs/pull/29/head -> origin/pr/29
* [new ref] refs/pull/3/head -> origin/pr/3
* [new ref] refs/pull/30/head -> origin/pr/30
* [new ref] refs/pull/31/head -> origin/pr/31
* [new ref] refs/pull/32/head -> origin/pr/32
* [new ref] refs/pull/35/head -> origin/pr/35
* [new ref] refs/pull/5/head -> origin/pr/5
* [new ref] refs/pull/6/head -> origin/pr/6
* [new ref] refs/pull/7/head -> origin/pr/7
* [new ref] refs/pull/8/head -> origin/pr/8
* [new ref] refs/pull/9/head -> origin/pr/9
$ git checkout origin/pr/35
$ make
$ git checkout origin