here's what I recommend if you are primarily interested in the aircraft themselves. (other books are available about pilots, units and battles/campaigns)
Soviet Combat Aircraft of the second world war
volume two : twin-engine fighters ,attack aircraft and bombers
by Yefim Gordon ,Dmitri Khazanov with Alexander Medved
ISBN 1-85780-084-2
$39.99 USD
Volume one is about single engine fighters and is
ISBN 1-85780-083-4 and is also
$39.99USD
they are both from:
Midlands Publishing Limited
24 The Hollow , Earl Shilton
Leicester , LE9 7NA England
after you have whetted your appetite with these I (and others) can recommend books on specific aircraft you may have further interest in.