This is the best available anthology on the important and difficult problem of clarifying and operationalising the use of character concepts in evolutionary biology. The introduction by Gunter Wagner, a leading evo-devo researcher and clear-minded theoretician, is the most cogent ten-page summary of the scientific difficulties and prospects involved you'll ever come across. The collection contains papers offering a broad range of perspectives: philosophical, mathematical, historical, comparative, mechanistic. All the papers are informative, and a number are simply excellent and evidently push science forward. I would go as far as to say it should be required reading for any evolutionary biologist.