If I were a Springer-Verlag Graduate Text in Mathematics, I would be Saunders Mac Lane’s Categories for the Working Mathematician.
I provide an array of general ideas useful in a wide variety of fields. Starting from foundations, I illuminate the concepts of category, functor, natural transformation, and duality. I then turn to adjoint functors, which provide a description of universal constructions, an analysis of the representation of functors by sets of morphisms, and a means of manipulating direct and inverse limits.
Which Springer GTM would you be?
The Springer GTM Test
As a side note, I weeded our collection of the Springer yellow math books last year. We had run out of space and they weren’t being used. The library purchased the series on standing order until 1992. After which point, only titles selected by the faculty were purchased. There were eight of them. That should give you an idea of how many of the others had been checked out even once over their tenure in this library. So far, no one has missed them.