His book "Numerical Methods for Scientists and Engineers" is brilliant, his work included information theory, sampling, and running bell labs during its most productive time. He wasn't a professor, he was a giant.
I also very much recommend "The Art of Doing Science and Engineering", which is mostly philosophical but has quite a few partial differential equations in it.
Available as a complete pdf here: http://worrydream.com/refs/Hamming-TheArtOfDoingScienceAndEn...