I second the Travel Trailer opinion. (or maybe it is third or fourth?)
My logic path:
You want a smaller truck, but slide in campers tend to be very heavy.
Truck will need to be a 1 ton and/or a 3/4 ton with a lot of extra suspension add-ons. ($)
The slide in truck campers are really small. Not a bad thing, just something to keep in mind.
Slide in truck campers (new) are almost the same cost as a Trailer. ($)
Your camper will always be with you. The plus is, you can leave anytime and just leave, (you don't need to go back and hook up) and you are likely to be able to boondock in a lot of places a trailer can't. (when in university, a fellow student did exactly this in the parking lot of the art faculty building) The minus, you will always use that extra fuel doing odd errands. ($)
The used slide in campers, tend to be used hard and put away wet. So, they are really diamonds in the rough, if you can find one in good condition. You may only find one to fit your vehicle from a dealership lot. ($)
My overall suggestion is to go to some RV shows/ RV dealerships.... Take the RV dealers words with a grain of salt... the experienced people here will tell you that the RV dealerships don't have the travel experience (they spend their whole summer selling, not traveling) to back up their claims that your truck can handle the weight. (I agree!!)
Read about towing in the library on this site. Read the posts and ask lots of questions.
Take your time looking.
See if you can rent something to test it first.
Camp in a tent or cabin and talk with RV people in person.
Honestly, when you get used to the height and size of a bigger truck; it's a little unnerving to drive a car again!! I prefer a full sized truck to a car now. When I drive my husband's Buick I notice the truck tires are right at the top of the windows!!