Yes! You can add captions to all Photo Books except the Mini size.
For all except the Mini, there are 12 different photo layout as well as the choice to leave the page blank. The ability to add captions is available on a handful of those pages. The ones which can be captioned have this illustrated in the 'layouts' section by a small line of black text underneath the upload box.
Do make sure you change the text on the front cover and delete any text that is not needed in any captions that you've added, as the default text will be printed if not removed. You will be prompted to edit this in the editor. The very maximum number of characters you should add is 200, but to be more legible we would suggest perhaps 160.
I'm afraid we currently don't offer full page text boxes in our photo books.
To find out more about adding you photos, click here.