If the book is DRM-free, you can open it in
Sigil and find the italics and see what is causing it. Sigil is free and there's a very active forum here if you run into any problems. If there's DRM on the book, you'll have to remove that first to make edits (Google Apprentice Alf).
I just about guarantee you're going to see there is a space there, it's just the illusion of no space because of the italics leaning into the space, as I've noticed on many books before.
You might try changing from full justification to only left justification to see if the spacing doesn't even out somewhat.