Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Unsurpassed pre-SPICE filter design reference

Zverev is the classic reference for continuous time filter design, especially lumped element LC ladder filters. The book is mostly tables, but the plots of filter behaviour for different designs--ripple, group delay, and so on, are easily worth the price. The discussion of how to synthesize a bandpass, bandpass, or bandstop filter from a lowpass prototype is very useful. They don't teach this stuff in school any more!