Try going to View -> Display Performance -> High QUality Display. You're probably at Typical. Neither view is going to be a bit-for-bit representation of your highres images, but at least in High Quality you probably won't panic.
You can also open up your Links panel and show link info (the little arrow in the lower-left hand corner of the panel, at least in InDesign CC) to reassure yourself by looking at the Actual PPI and Effective PPI.
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Actually, after a closer reading of your original post, you should also make sure your images are still linked in your Links panel - if you see a red circle with a question mark, then ID can't find your image file and is exporting a 72ppi preview. Also you should look at the settings in your PDF Export preferences; for a photo book I'd personally start with the Press Quality preset, then turn off all downsampling (so that any downsampling necessary could be managed at the RIP).
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