I would recomend starting with an aquacultured species. There are many to choose from.
Seahorsesource.com has quite a variety.
Minimum tank size would be a 29g IMHO. You want to keep the temps cooler 70-74F.
The current in the tank needs to be gentle and spread apart so there are no strong areas that will blow the seahorses around.
Tankmates need to be non aggressive both with fish and corals.
They only need enough light to see there food, if you want to keep plants and corals, then you will need more light depending on what you want to keep.
HTH
Any specific questions we'd be glad to help. Sorry I know of no up to date books. For some reason the publishers don't want to invest in one.