There are a ton of MOSS books being published right now. If you are a developer and looking for one; hands down get Microsoft SharePoint: Building Office 2007 Solutions in C# 2005 by Scot Hillier. Scot’s book discusses all of the things you will need to do day one for as a developer from a SharePoint project. He provides step by step instructions on how to create site templates, web parts, features, SSO, object model stuff, some administration, fundamentals and he actually provides an example of a how to create a custom workflow that works. I had messed around with writing WF flows throwing them into MOSS during beta timeframe and failed miserably due to the complete lack of documentation (I would still not go off the deep end and create core workflows in MOSS). Although the workflow he provides is very similar to a free virtual lab I did some time ago. Try it out.
If you want to get Microsoft Office SharePoint Server 2007 Administrator's Companion by Bill English. This is a fine book but most of the information you can get for free on MSDN.
Also if you want to get good training on SharePoint I highly recommend attending a training session with MindSharp.