This book gives a leisurely and clear exposition of the main topics of discrete mathematics. it is a translation of the 5th (2004) German edition and reads very smoothly, with only a few translation glitches.
The book assumes a moderate amount of mathematical background and maturity and in American terms is probably aimed at upper-level undergraduate classes. It assumes a familiarity with proofs, although the emphasis is on discovery, concepts, and techniques. The intended audience is both math and computer science majors.
Compared to the popular texts, Rosen's Discrete Mathematics and its Applications and Ross and Wright's Discrete Mathematics, Aigner covers very nearly the same topics, although in half the space (and half the cover price).
This conciseness comes primarily from having many fewer worked examples, typically only one per section versus a half dozen or so in the other texts. Aigner makes up for this by having many more (and more challenging) exercises. There are about 550 exercises, and about 1/3 of these have solutions sketched in the back of the book. I like this approach, where the author gives you just enough information to get started and depends on you to work the exercises to master the subject. But this is more demanding than the typical American textbook and may not be popular with everyone.
Allen Stenger is a math hobbyist, library propagandist, and retired computer programmer. He volunteers in his spare time at MathNerds.com, a math help site that fosters inquiry learning. His mathematical interests are number theory and classical analysis.