something just came to mind Ziggy. I really don't have a solution for creating multiple lines on a single word document for a dynamic number of records (that could change at any time). Although I do think this is possible, I've never programmed it.
But another slick idea might be changing your 'books' field to a memo data type. If you do that you can keep your merge document exactly the way you have it now (with one 'books' field) and merge it as normal with your Access records. The catch here would be to use the memo field to store the books with a 'vbcrlf' delimiter. I think this works, although I haven't done it quite a long time. Try entering your books into a memo field first by typing. Close the form and let the table refresh itself, then open the record back up and see if it condensed the new line characters.
If that doesn't work, you might want to try entering your book names through a control of somekind and using code to insert 'vbcr' or 'vbcrlf' after ever book name. Does that make sense? I'm almost 100% certain that a memo field will store the format of the data. If it does, you'd be in good shape because the word document simply reads Access data 'as is' when it's brought in. That's been my experience anyway.
Give that a go...that's my suggestion to you.
