I think you can still access and use your account when it is on hold, it's just that it becomes invisible to other people.

Here is the info from the Help Center--It looks like you can still request books ( I think Ive read of others who do this..they put their bookshelf on hold after spending their postage budget but still able to order books)

How does the Hold affect your Bookshelf?

• The books that are on your Bookshelf at the time the Hold goes into effect will be hidden from requests.

• This does not include books that are involved in a Wish List Hold or an active transaction.
• The FIFO order of each book will be preserved during the Hold; it will not "lose its place in line" to get requested.
• Books that are already involved in an active request will not be affected by the Hold.
  • Any book request that was submitted before the Hold went into effect will not be affected by the Hold
  • Any book request you submit at any time (before, during or after the Hold will not be affected by the Hold. (underline & bold added by me)
• This means that all auto-emails associated with an active transaction will be sent to you as usual
  • You will still get auto-emails asking if you have received a book that is en route to you 14 and 21 days and 25 days after the book was marked mailed by the sender.
  • You will still get "second" and "third" notifications for previously-submitted requests to which you have not responded.
  • You will still get auto-email reminders to mark your outgoing books mailed before the deadline if you have not done so.

Julie, yes indeed you can order books while you are on vacation hold.  I just did that myself recently.  You can access anywhere on the site, the vacation hold just helps to prevent you from missing requests for books or wish list books.  You can however put any books from your wish list that you want to get anyway on auto-request.  The system will automatically order the book for you if it becomes your turn to get the next available copy as long as you have a credit to order it. 

Oddly enough, I could not order any books whilst my shelf was on hold. I had thought I could still shop even though I couldn't send out anything, but I couldn't.

Okay, I'm not 100% getting this from the Help Center description.  When your wish list goes on hold, do you keep moving up in line for books with a long line and just get bumped when you get to #1 - i.e., if I'm 200th in line for The Thirteenth Tale and 10 copies get posted, do I move up to 190?  Or do I just stay in line at 200?

Hi Kristin!  I request books all the time when my shelf is on hold.  You do still have to post when you receive them, though, so you should make sure you have access to a computer on your trip. 

My Wishlist is on autorequest so if any book comes up while I'm away and my shelf is on hold, I still automatically get them if I'm next in line.  Since they're on autorequest, I don't need to respond when they come up, it's done automatically.  This summer I was visiting family in NY for a month and when I got to the local library to check my PBS acc't, THREE wishlist books were on the way! 

I am not sure what happens if your list is NOT on autorequest.