I have, by mistake, caused all my photos in a large book I am making to revert to the original. This after a long time spent editing etc. I don't understand how iPhoto library works. I have aTime Machine. I also have an EHD backed up 2 days ago.

Yosemite 10.10.3

i am making a photo book with iPhoto, had already started it when Photos superseded iPhoto so I carried on. Have spent a lot of time on it, it's a large book.

BY mistake I caused all the photos to revert to original.

I have Time Machine and I backed up Photolibrary to EHD 2 days ago.

BUt it I don't understand iPhotos library. If I replace existing library from Time Machine, all my projects, albums etc. be there as they were before my BIG mistake?

I have read that Time Machine is not suitable for back ups of iPhoto so should I try to use my EHD? In finder it just shows 'iPhotoLibrary'. So the same question arises - does the Library incorporate all my projects and the work I've done on them up to the date of back up?

I would be so grateful for help and advice