For me, after a year or more I still read some portion or another of this book nearly every week for the rich survey of ideas and theories it provides, often finding something that fits what I'm concerned about, and then springboarding into buying another book or digging out original research articles and papers to dig deeper.
If you want to be widely informed about the full continuum of theory and research in leadership and organizations, this book will become a familiar resource, and a top choice for curling up to a fire one evening when alone and just paging through and finding something new or old you just have to read and think about some more.
Okay, perhaps Marc is more of a fun guy than me, but everything about leadership, and this book is full and pressed down overflowing with the material, interests me deeply.