This book is actually a translation from the Russian Frontline Illustration series.
The T-39 was a heavy tank project designed to the late 1920's standards for a heavy tank intended for breaking through permanent fortification lines. Such a vehicle was to be armed with a 107 mm gun or a 152 mm howitzer, was to be capable of firing at at least two targets at one time and have an armour protecting from divisional guns. Six variants were designed in 1933, and - after comparison with Grote and Ansaldo projects - three more were created and built as 1:10 scale mock-ups (known from the photographs). It's hard to say which version is which, as they are mixed again and again by different authors, but it seems the version no. 8 was chosen for further development - it was to be armed with one 152 mm howitzer and three 45 mm guns in four separate turrets. The tank was to be some 90 t heavy, have 70-75 mm armour and reach 24-33 km/h with a 970-1300 hp engine (a steam engine was even concerned).
What's interesting, the T-35 heavy tank (favoured by Voroshilov) wasn't actually a heavy tank as far as its armament was concerned, but - along with the high cost of the prototype - it was probably one of the reasons of cancellation of the T-39 project in early 1934.
Regards
Grzesio
