driver types

maybe in the wrong forum here, but someone might know.

i have a device that sits on the ISA bus (it is not plug and play), it's kind of a data acquisition card. i want to write a driver for it to work on win98. which type of driver would be best for this task? a .wdm or a .VxD or what?
can anyone help and give me a little bit of info on this. or maybe recommend a decent book on the subject (the only one's that i have found either deal only with win3.x and win95 or the WDM only [which is only PnP, i think]).

cheers, BigDaz.