Hello,
New member here.
How can I rearrange the order of my images?
Also, I was confused as to the difference between a book and a gallery.
How can I delete a book since I don't have anything in it?
Thanks in advance for your help.
EYElene

taken from the modelrun wiki:

Books

What is a “Book”
A “Book” is basically a portfolio, but when a portfolio could become pretty big and not really targeted, a book should contain only your best work (as a model or a photographer) - the best of your best photos, arranged into categories (books) of your choice. All members start with just one book, but by earning ModelRun badges you can “unlock” and have up to three different books.

Emailing Your Book
Your ModelRun "Books" give you additional options, like emailing directly the desired book to a client or agency (or to multiple recipients simultaneously). Your additional information (model stats, screen name, etc.) will be added to that email as well, so you don’t have to type it. This feature is very useful also because it lets your email address remain private.

Applying for Castings with a Book
You can also apply for a casting by directly using your book. We decided to give our members 3 books (and not just one, like in real life) because you, as a model or photographer, may want to apply for completely different castings/markets. It is really important that you always send the right book – exactly the one that the client would expect and care to see. As example, there are many models that can do both fashion and glamour, but if the casting is for a bikini calendar, the client would not care to see fashion or any other shots. And like with emailing your book, your email address will remain private.

Exporting Your Book
You can add a Book to your MySpace or Facebook page or any other website as a cool slide show, linking directly to your ModelRun profile. It will also self-update every time when you change it here. By using this feature you are also contributing to the growth of our community.

Book Slideshow
This is just a simple but convenient feature that lets the viewer preview your book as a slideshow.

Private Books
You can make a book “Private”, which would let you choose which user to give a permission to view it to.

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PS: you can't do any of these with a gallery. your gallery is just a folder with pictures.