If you are starting with WSS and/or MOSS 2007 then I must recommend this book.
I just finished it and I am very glad I did. I gives you a clear overview of WSS and MOSS and explains the difference between the two products and when to use which product. Luckily th eauthor has a good sense of humour making this book an easy reader.
So check it out.
Beginning SharePoint 2007 Administration: Windows SharePoint Services 3.0 and Microsoft Office SharePoint Server 2007
by Göran Husman