1. A computer-implemented method of generating a custom dictionary for an e-book, comprising: receiving a custom dictionary request from a user client operated by a user, the custom dictionary request identifying the e-book and including dictionary management information describing the user; choosing a group reading profile, having an associated group reading score, for the user based on the dictionary management information; identifying candidate words in the identified e-book for inclusion in the custom dictionary; selecting words for inclusion in the custom dictionary from among the candidate words responsive to the associated group reading score for the chosen group reading profile; generating the custom dictionary using the selected words; and providing the generated custom dictionary to the user client.