It is a living, non-abelian entity. And it is hungry for the next lost soul who dares to look at Problem 14.7.10: "Describe the lattice of subgroups of the quaternion group Q8."
The book is almost certainly Abstract Algebra by David S. Dummit and Richard M. Foote. Weighing in at over 900 pages, it is the undisputed heavyweight champion of graduate algebra texts. It is comprehensive, rigorous, and notoriously difficult.
Pedagogical approach
The solution manual for Abstract Algebra by Dummit and Foote is not officially available for free online. However, there are some draft write-ups and unofficial solution manuals available on various websites and online platforms.