The variation of the French that starts 1 e4 e6 2 d4 d5 3 Nc3 (or 3 Nd2) 3 ... dxe4 is often called the Rubinstein Variation. It is a great way to simplify the position and ensure that the middlegame battle rewards strategic understanding rather than rote memorisation of opening moves. It is also a very useful weapon to defuse the attacking intentions of aggressive White players who plan an all-out assault in the main lines of the French Defence.
An important feature of the lines after 3...dxe4 4 Nxe4 is that Black has various different ways to continue. 4 ... Nd7 is the most common but 4 ... Bd7 (planning ... Bc6 – the Fort Knox Variation), 4 ... Be7 and 4 ... Nf6 are all possible. All these lines are covered in the book.
Finally, White can, of course, avoid the 3 ... dxe4 variation with (amongst others) the Advance Variation, 3 e5. Martin provides antidotes to all these possible sidelines and so the variations in the book provide a complete repertoire to meet 1 e4.