The Forgotten Battles is a very good description as most histories of the eastern front that I've read are concerned with what happened to Operation Blue during 1942 and largely ignores AGC's front.
Just read quite a bit on these battles on this page:
Here's a quote from Zhukov on these operations:
Today, after reflecting the events of 1942, I see that I had many shortcomings in evaluating the situation at Vyazma. We overestimated ourselves and underestimate the enemies. The "walnut" there was much stronger that what we predicted.
—G. K. Zhukov
Here is the summary from the German side:
After the Soviet winter counter-offensive of 1941–42, the Germans were able to strongly hold and defend the salient against a series of large Soviet offensives. The operations led to disproportionately high Soviet losses and tied down large numbers of Soviet troops. The defense of the Salient provided the Germans with a base from which they could launch a new offensive against Moscow at a future time. The defensive positions created by the Germans after the retreat from Moscow were well constructed and placed.
The Germans eventually withdrew from the positions only due to losses elsewhere in the war and were able to withdraw from the salient with minimal losses.
German operations in 1941 directed at Moscow lasted too late into the year. Rather than stabilize the front and create defensive positions, the Germans pushed their forces forward and left them poorly prepared for the Soviet winter counteroffensive. The losses in men and equipment to Army Group Centre were considerable. The Army group lacked the strength to go back on the offensive in 1942.
After the front stabilized, the German Army tied down enormous amounts of manpower in holding salients from which they did not intend to exploit. This reduced the amount of manpower the Germans could devote to operations elsewhere on the front. The Germans also used some of their best formations, such as 9th Army, in a strictly static defensive role. The Rzhev salient had value and tied down disproportionate numbers of Soviet troops, but it is unclear if the salient was worth the loss of around 20 high quality divisions for offensive or defensive operations elsewhere in 1942.
The abandonment of the salient was necessary in 1943 to create reserves for the front as a whole. But the reserves and the strength created were mostly used up in the costly offensive directed at Kursk in 1943.
These positions must have been strong as the German salient looks incredibly vulnerable from a map reading point of view to a pincer attack between Vyazma and just north of Juchnoff by the Soviets