The Oxford Handbook of Medical Dermatology is a great little textbook of dermatology, with opening chapters on skin structure and function, history and examination. Whole chapters are devoted to eczema and psoriasis, and skin cancers, as well as infection/infestation, emergency dermatology and dermatology relating to other specialities (this list is by no means exhaustive, consult the contents).
While not as comprehensive as the bigger and more expensive dermatology textbooks, it covers a broad number of topics in some depth.
Unlike other Oxford Speciality textbooks, there's a number of colour illustrations and photos, but not as many as you'd think or for every manifestation of dermatological disease. If you are looking to diagnose dermatological disease, "Differential Diagnosis in Dermatology" would be better for you, but where that book lacks is in treatment options, the Oxford Handbook of Dermatology excells. For any interested student or doctor upto registrar level, owning these two books would go someway to de-mystifying dermatology.