Definately looks really thin. Follow stricter then normal acclimation suggestions. Also, if he's really lithargic, I'd get him to the vet to see if somehting can be given to him for appetite stimulation. You can also force feed him yourself to get his appetite and weight up. Here's some info:
Acclimating and Introducing Uros
Acclimating a new uromastyx is a vital part of helping to ensure that it gets to, or maintains it's healthy status. Incase you're not sure what acclimating is, it's helping to ease the transition of the uro going from one environment to another. This typically is addressed when a new uro comes to your home from either the wild, a breeder, or a pet store. During this period of acclimation (anywhere from one to six months), the uro should be in the most stress free environment as possible. This not only comes from the enclosure and surroundings stand point, but also as to how you treat it.
Things that help with acclimation include, but not limited to:
* Placing the enclosure in a low traffic area of the house
* covering three sides of the all glass tank so that the uro only sees out the front
* When possible, get an enclosure that opens in the front rather than entrance from the top
* Have multiple satisfactory hides to provide as much stress free area as possible
* With multiple hides, have them in different temperature areas
* Change out and feed the uros after they've retired for the day
* Do not handle the uros unless it's absolutely necessary
* Look for eating regularly and gaining weight as good signs of acclimation
There may be other things that you find that work, but you can see the goal here.
Depending on the source form which you got the uro, a vet visit wouldn't be a bad idea to have it checked out for any health issues that you may not be aware of. Be sure to do at least the minimal research on the vet before going in. Usually they will tell you if they're not familiar with uros and maybe tell you of a local herp vet that is.
Needless syringe feeding
When Rocky appeared to "come down with something," I'd just maxed out my credit card trying to save my female, so I was determined to do what I could on my own. He stopped eating, then, as he had in the past, he started to get lethargic, not moving around too much, and eyes closed most of the time. Last time this had happened, two big shots of fluids and a tube feeding turned things around. So I took it upon myself to head to the grocery store and get those baby food jars that read just like my uro's dinner list. The vet gave me a 6cc syringe without a needle (let's face it, I wanted to help, not make things worse), and I also picked up some pedialyte at the store. Twice a day to start, I'd take take a shot glass, not that I had any, and go 50% pedialyte and 50% baby food. Stir it up and place it in a water glass of the hottest tap water I could get. Once it warmed up, took him out and have everything ready to feed. Then, with a full syringe (6cc for a then 88 gram geyri) I'd work it in between his "lips" by the hinge of his mouth. Once he'd get a taste, he'd start "lickin' his chops" and that's when I'd put the whole tip of the syringe in his mouth, and start feeding it in. I found it easier if I held him at a 45 degree angle, as he would start to open his throat area, and the whole contents of the syringe would go in. I don't really think he'd swallow it until later, but as long as it wasn't coming back out, I was ok with it. He didn't stress or dislike it too much, as after, I could set him down on the couch, and he'd stroll around instead of running.
I did this twice a day for about 1-2 weeks, then I would start to wean him down to once a day (twice a day here and there if I thought he'd take it in). Also, I'd start going with a bit more food and less pedialyte. Eventually, in about 3-4 weeks, it was very noticeable that his energy, weight, and appetite came back. I now keep all the necessary stuff here incase I need it again.
This is just a thought and not saying that this will help, but I can't see why it would hurt. Rocky's now plump enough that he looks like he's "puffed" up in defense (little fatso). The heaviest he's been before this, was 118gm, and as of mid May, he weighed in at 154 gm!
(Note: The feeding with a needless syringe was done with Rocky because, for reasons unknown, he stopped eating, which caused his metabolism and energy to drop, cause dehydration, which in turn caused him to feel bad, therefore not to eat, and it spiraled down until he was outright lethargic. Only then did I resort to the baby food/pedialyte through the syringe.) I plan on video taping the feeding that I've done so people can put a "visual" to the attempted explanation.
-----
2.1 - Rocky, Runako, and RoxyIII (my care sheets)
Kelly Wood 
Everyone has had good advice, its just when I see a Uro that is that thin, and already lethargic... well, I feel the need to do the "Vet Dance" 
