If a book doesn't import after you used Import Books then it will be for one of two reasons. Firstly, that Amazon did not list the book so we could not import the data. Or secondly, that they list the book but neglected to add any food or drink tags. We had to add that second criteria as we have had members import the ISBN numbers for their entire book collections, many of which we would not want appearing in the EYB Library.
You can see which reason for the non-addition of your book by looking at My Added Books under the Bookshelf tab. The options in the green search bar are 'Imported', 'OnAmazon' (but not imported as missing tags) and 'NotOnAmazon'. For the latter two you need to manually add the book using Add Member Books, again under the My Bookshelf tab. There is more information on adding book data here in Help.
I added The Philosophy of Puddings to the Library for you - it is now on your Bookshelf. Jenny and I do try to keep on top of adding requested books not imported because of missing tags but when we are overloaded (as currently) we can get a bit behind.