"Let's read a book."
Translation:Leggiamo un libro.
This is a distinction between the imperative form and simple present form. Interpreted as simple present, both "Noi leggiamo ..." and "Leggiamo ..." translate to "We read ..." In English, when you say "Let's do something", it is expressing a command, and so the imperative "noi" form is translated to "Let's ..." This would be difficult to interpret from Italian to English, because the Simple Present and Imperative "noi" and "voi" (and some "tu") forms are identically conjugated.
Hi! Just curious ... where were we taught this difference? I don't remember a lesson prior to this practice session on the difference between imperative and simple present tense. I'm sure glad you wrote to explain it. I just want to know where I missed it in the sessions up to now. Thank you!!