The book section on the website is only available for SW members, from what I can see.
It may be worthwhile joining, going to class to get the pack and the talk, and you could buy whatever they have there.
You could then buy whatever they have on for sale at the website.
You wouldn't have to go back but will have everything you need.
If you are a group member you can also order them over the phone directly from SW. You used to also be able to do if you didn't belong to a group but they changed the rules last year and this is no longer the case. If you do a search here for Book Enquiry Line you'll find the telephone number to ring.