Here is an unsolicited non-review from Ewart Shaw.
Here are lots of extra exercises to support Topics in Group Theory. Model answers are available on personal application by bona fide instructors. If I catch any student trying to trick me into giving him or her answers, I will immediately grass him or her to the relevant Principal or Vice-Chancellor. The punishment for cheating at proper universities is head on a pole in front of the library as a warning to the others.
You may be interested in other books published by Springer. Templates for making paper models of the Platonic solids may be downloaded from here. The designs were crafted by Aaron Wilson.
Here is a record of gremlin achievement.
|Corrigenda for the 1st printing|
Geoff Smith has written or edited some other books. There is a virtual tavern group pub forum associated to a mailing list for the group theory research community. Please do not trouble the people on this list with undergraduate homework problems. The archive of correspondence may be helpful if you are thinking of following group theory beyond Topics in Group Theory.
There are also Computational Group Theory systems available. The most well known are GAP and Magma. Another excellent group theory site is the MAGNUS software project (containing an interesting list of open problems).