Lions' Commentary on UNIX 6th Edition, with Source Code

Here's another vote for K&R. If you want to understand why C and UNIX were so successful, it comes down to simply excellent communication. And remember - no web, no internet, no WYSIWYG word processors, etc. at the time. To appreciate C properly, I think at some point you need to become a bit of a historian. Look at BCPL. Look at what assembly listings looked like or old Fortran. Read some of the very early papers from C and UNIX history. Check out Lions' commentary on UNIX. When you see a little of the problem C was invented to solve, it becomes a lot easier to understand why it is what it is. There's a lot of angst about why C allows Bad-Thing-X or doesn't have New-Fancy-Thing-Y. Nobody seems to remember what a change it brought to writing systems code. Then you can compare it to things written in modern C (C99+) and see that yes it has evolved quite nicely and can, if used correctly, be a nice application language too.