L4 Microkernels: The Lessons from 20 Years of Research and Deployment, a retrospective explaining how we got to where we are;
UNSW Advanced OS lecture slides, especialy the Introduction and Microkernel Design lectures
Release download page for the current release.
Manual for the current release.
Building the manual for a specific version
To get the latest version of the manual, checkout the seL4 source code then:
cd manual && make
You need LaTeX and doxygen installed, and if all succeeds a fresh manual will be produced in manual.pdf.