And his signature is rather clear - though looks like "Jim" - and he must use a flourish on the final "L"..
I think the entire first name is a squiggle, unless it's one we haven't considered yet, but it doesn't look exactly like John, Jean, Juan, Jason or James/Jim. Assuming each letter is formed, I count five peaks (too many for "Jim") and four troughs. So when it comes to signatures, it's often more useful to guess than it is to read. There's a D in my name but when you look at my signature, that D is reduced to a single vertical line.
It's also possible that the capital letter of the surname moves back through the first name in an attempt to cross an "A" there (so "Jean/Juan"?)
The only thing I'm sure of is that the first name starts with J and the last name ends with "allo". There's no way that final letter is just a swash for the second L.
As for the other letters, well, it could be any combination of Us, Ms, Ns, Rs... Or squiggled Es, As, etc. If you look at the way he wrote "Paris", assuming it is Paris, it's clear that his Rs look like Ns.
I wouldn't pay attention to the extra bar on the 7. I regularly see it written this way in Ireland and the UK. I think the format used to write the date is much more significant, and it's definitely American/UK. No French person would write the date in this manner.
Here's a final thought: How about a woman? In that case, the surname could be misleading and blur that person's connection to the book's subject or its author (maiden name? Married name?), and deciphering the first name would become key. So could it be a Jenna? A June?
Good hunting!