My Lonely Planet book references an overnight train from Bangkok to Phuket, but then doesn't provide any additional information it. Does any one know where I kind find more information on this?

Or is by air the best way to travel between the two? I liked travelling by train in Europe and thought it might be a fun alternative to flying which has less character.

I think you may have mis-read something. There is no train service to Phuket (it is an island after all). There is overnight bus service, which is faster than the train would be anyhow.

Trains in Thailand are nothing like they are in Europe. While train travel can be interesting, I don't think it's worth the time it takes, and budget airlines can get you where you want to go for about the same price.

Correct, no trains to Phuket, an overnight AC coach is the cheapest, if you check out the travel agents there are some cheap air tickets as well. Flying is probably the best way now.

You can catch the overnight train to Surat Thani and then a 4 hr bus trip to Phuket. A 2nd class a/c lower berth plus bus ticket will be around $23us. A 1st class compartment will be about $35.

Flying on dicount airlines Air Asia will cost on the average $43 net.

2nd class (non AC) berths are also great and cheaper.

There is a train departs Bangkok daily at 19:15 and gets to Surat Thani at 06:40.

You will be met at the station by people guiding you to the (overpriced) buses.

The direct buses from Bangkok to Phuket are comfortable, but the drivers often live in their buses (with their families) and work too many hours, the main North/South highway is of excelent quality, this helps the drivers go fast, but the ride is very smooth and too many times I watched the driver as he seemed to be falling asleep.

If you do get the bus, when it stops for a meal break, walk arround the corner to an alternative food place, the drivers have a tie-up with the places they stop at, so the food tends to be 'westernised' (read awful) and overpriced.