IMHO, Mr. Walt Jung is one of the greatest engineers of analog electronics of all time. His IC Op-Amp Cookbook is a must have for any engineer who uses Op-Amps. I personally own two copies, the 2nd edition I bought in 1980 and the updated 3rd edition I bought in 1990. Unfortunately the currently available print editions are reported to be very low quality that is why the link above is set to find an older printing (like my newest copy). See the books page at Mr. Jung’s site for more information about this and his other excellent books.
The library section also contains PDF’s of many of Mr. Jung’s excellent articles and even a complete book written for Analog Devices. I am particularly excited to find his articles from The Audio Amateur magazine as I had to part with my complete TAA collection due to space constraints when I moved last year. Mr. Jung’s writing in TAA was one of the primary motivations for my career choice of electronics design especially my favorite work, analog circuit design. A very important lesson that was driven home from his TAA writings was the need for rigorous scientific methodology in assessing analog circuits especially audio circuits. The audiophile world has always had people who fall for pseudo-science, The Audio Amateur and especially Mr. Jung did a great job of debunking pseudo-science with science whenever it reared it’s ugly head.