The series concept is fresh (there are not many series featuring a djinn), and the story is compelling, but there are a few problems, mostly in book 1. The Donatti—Jazz relationship is one of the weakest elements in the book. In book 1, they haven’t been in contact with each other for three years, and much has happened to both of them, but they get right back together—it’s just too easy. Also, at one point in the same book Jazz’s sister is incinerated in a house fire, and in the next scene Donatti and Jazz are making out in the back seat of a car. I don’t think so! Jazz doesn't have many scenes in book 2, but the relationship (what little we see of it) does seem somewhat more realistic.
Another problem occurs with the powers of Ian and Tory—again, mostly in book 1. Sometimes they can do wondrous things (e.g., fly, produce things out of thin air, turn an old clunker into a new sports car), but other times they can’t (too tired, power drained, etc.). The down times cannot always be logically predicted; they just happen when a plot twist needs them to happen. This does get better in book 2.
The violence level is high because of the frequent torture scenes. In book 1, few graphic details are provided, so the rating is 4. In book 2, however, the excruciating details are extensive and continuous.
The humor comes from the sarcastic dialogue between Donatti and Ian and from Donatti’s constant wisecracking (even—unbelievably—under extreme torture). This also is handled better in book 2.
By the end of the second book, Donatti was beginning to remind me more and more of Rob Thurman's CAL LEANDROS (UF—V5, S3, H4), which is one of my favorite UF series. Cal and Donatti have the same disillusioned, hard-luck outlook on the world, but they never give up, even in the face of extreme pain and constant frustration. By the end of Master and Apprentice, the relationship between Donetti and Ian is very similar to the relationship between Cal and his brother.
If you love djinns, you might also enjoy Rachel Caine's WEATHER WARDEN series (UF—V5, S3, H1) and OUTCAST SEASON series (UF—V4, S2, H1) and Mindy Klasky's AS YOU WISH series (SMR—V1, S3, H4), all of which feature djinns as main characters.