Well worth having, but investigate before buying whether Home or Pro will be best for you.
Having read the relevant part of it, I realised I'd bought the "wrong" manual. I should have, and have now also bought, the "XP Home" manual as more suitable for my needs, because the "XP Pro" manual deals additionally with the greater complexities of Networking, which are not my concern.
However, both manuals are clear and comprehensive, and answer the questions that come to mind, together with many extra helpful hints. Quite as good as any other brand of manual I've had before, and better that Microsoft's own, I'd say.