"She is the woman in the book."
Translation:Lei è la donna nel libro.
I believe nel is (in + il) and nello is (in + lo)
For an explanation on "lo" see the link below:
Also, here's a chart of how all the prepositions are formed:
I'm new to Italian too, but knowing some French helps pick up some of these concepts. Hopefully someone with a higher level can clarify.