Probably closer to 3 1/2 stars.
I really liked the earlier books in the Immortal Guardians series and Naughton's writing is, unshockingly, similar in this one (that's a good thing, I like her writing style.
This series has much the same, hot, bloody, tortured (literally) heroes, this time djinnis, a big bad villain, some angst and some steamy scenes. Each book would've benefited from being longer. The characters just fell for each other way too quickly; if the books were longer, a little more time could've passed (more getting to know each other and action, less lust). There could've also been a little more will/can they trust each other or not type of tension.
I did like that the author went with djinnis and liked that there were different types. I'd actually be interested in reading another book set in the djin realm with a Ghul guy as the main character.
If you like Elisabeth Naughton's Immortal Guardian series and her writing style, I'd recommend this box set (I'm not sure how long it'll be this price, but I got it for 99¢ on Amazon).