J. Carcopino provides a malicious portrait of Cicero in his "Cicero : the secrets of his correspondence" (English translation in 1951).

Since he often quotes out of context it is difficult to follow him without question, although I'm not a fan of Cicero.

His thesis : the letters were published at the secret instance of Octavian in 33-32 with the purpose of discrediting Cicero to justify his proscription. In his work, Carcopino has gathered many evidences of Cicero's fortune and extravagance, vanity and selfishness. It's a distorted point of view but interesting nevertheless.