What the others said. Plus, I personally like the .45acp, in the small frame sizes. I have a Kimber ultra carry, and absolutely love it! Any of the other small framed .45's and nine mm in that size, by Springfield, S&W Glock, Ruger,and other brands are fine also. If you like 9mm's there are a bunch of choices to choose from. The Kel Tec, Diamond Back, Khar Arms, Astra, Baretta, Taurus, Colt, S&W Ruger, and others.
The Ruger LC9 is compact, and thin. I would reccomend a good hollow point bullet for whatever gun you choose. Like Federal's Hydra Shock. There are other brand and types that are effective also. The Ruger LC9 is a double action auto, meaning, you have to pull the trigger in a double action mode, and when fired, it will "automatically" put another round in the chamber. It the safest as far as pocket carry. The only draw back to it that I have with it, is the long trigger pull. Same with the LCP, in .380 acp. I have a LCP in .380 acp, and it shoots very well for such a short barrel. I have a Crimson Trace laser sight on it, not so much for sighting, but more as a psychological advantage. The idea that you have a red, or green dot on you, kinda makes you think twice about life in general.
In a low light situation, it can put your barrel in the ball park. I carry the LCP, mostly, but still prefer the Kimber. It depends on your financial situation, but try to buy a well known brand, that is know for RELIABILITY, and customer support. When it comes to price, what is your life worth? Or your family's? By all means, when you finally select one, get an extra clip, or two, and PRACTICE with it at the range, and practice with it unloaded, by pulling it out from where ever you have it concealed, and be able to do it smoothly, and as unobtrusively as possible. If you can't do so, try another position. Practice often, even though you may be able to remove it quickly, and easily, you need it to be an automatic response when you need it, not having to think about it. You may have it hidden, with no print, and feel quite comfortable with it, till you have to pull it, and the time to find out how fast, and smooth you can bring it into action, is not when you actually need it! A lot of people carry a gun, and feel quite confident with it's location, till they have to use it, and in a life or death situation, fumbling around trying to get your cards on the table, when the bad guy already has his laid out, is not a good game to be in.
There are a lot of options for concealed holsters, and carry systems to choose from. this is all "Just my humble opinion."
Wayne