Charcoal canisters are cheaper but only do a short-term snapshot. Get an alpha-track and do a long-term test, which gives you a much more reliable picture of your exposure. You can absolutely do both. There are also continuous monitors which are more expensive still, but some folks just love live data.
If you hadn't mentioned neighbors on both sides, I'd say as a slab-dweller, you might be worrying too much. But that definitely points to uranium in the local soil, and while slabs are generally at significantly lower risk than basements, your situation is one where it's definitely worth testing!
We went with https://www.homedepot.com/p/Airthings-Corentium-Home-Battery... which the other commenter suggested as a more expensive solution.
I bought this because California county Radon maps showed us in a "tan" area, meaning "moderate" risk of Radon above 4.0. Here's an example of one such map: https://www.conservation.ca.gov/cgs/Documents/Publications/S...
Note that radon levels varied greatly in our house by both weather and time of year.
1: https://www.homedepot.com/p/LABTECH-Radon-Detection-Test-Kit... 2: https://www.homedepot.com/p/Airthings-Corentium-Home-Battery...
Follow the instructions to the letter (use the hole, tie a string to it and suspend the test in the middle of the room, in an area away from traffic and away from air currents).
I recommend using two, on opposite sides of the room.
Then leave it there for a year. Many places have seasonal variation in radon, so while you can do a 3 month test, I recommend a 1 year test.