
If you want the big and surely totally unbiased view, Helion & Co. sell (both in hardback and in ebook format) the book Rollback - The Red Army's Winter Offensive Along the Southwestern Strategic Direction 1942-43, written by the Soviet General Staff. Here is a quote:
"The Soviet forces’ crushing attacks in the Northern Caucasus,
along the Rostov and Voroshilovgrad axes, and around Leningrad
tied down the German-Fascist army’s forces, distracted to
themselves the Hitlerite command’s reserves, deprived him of the
opportunity to reinforce his Ostrogozhsk—Rossosh’ group of forces,
and thus created very favorable conditions for the Voronezh Front’s
conduct of the offensive operation."