Well the Western Front in WWI was far smaller than the Eastern Front in WWII. The Western Front stretched from Flanders in Belgium to Central / Southern France. At the height of German advance, so circa summer 1942, the lines extended from roughly Leningrad in North West (if we are excluding the occupation of Northern Norway in the Arctic Circle / some minor involvement with the Finish in the Arctic), Russia down to the Caucasus in Southern Russia, that is a huge swath of territory. Also, the WWII front lines were very fluid, with battles raging all over. The Western Front was densely populated with troops. You could barely scratch your unwashed nuts without rubbing up against a fellow soldier or two. There was barely enough room for you. So when artillery strikes happened, and a buried a trench in a direct hit, a lot of soldiers died. The same could be said in certain situations on the Eastern Front in WWII, like the Rattenkrieg ("Rat War") that was the Battle of Stalingrad, where troops were literally on top of eachother (like in many cases you would have German troops occupying one floor of a building, the Soviets on the floor above or below, Germans, Soviets etc...). There was a lot of dug in protracted trench warfare on the Eastern Front - but no where near the amount on the Western Front in World War I.

If anything the trench warfare on the Eastern Front was different in the sense that each unit had to cover so much territory that units were spread very thin. A raiding nightly patrol could sneak up to your trench or foxhole in the middle of the night, capture you or slit your throat, without your fellow comrades close by even noticing - that certainly was not the case in World War I.

However, ferocity-wise the Eastern Front was worse in some regards. Sure it wasn't stationary warfare (most of the time), stuck in a muddy trench with hundreds of your comrades, with constant enemy shelling... but there were times like that on the Eastern Front. Artillery was the largest killer of both World Wars. But the ferocity was different on the Eastern Front because unlike World War I, the Russian Front saw armies collide that HATED eachother. That believed the other was ideological, politically, and inherently evil. There was so much Ant-Communist propaganda and hate on the German side, and vice versa for the Soviets. Both sides fought to utterly destroy eachother. Whereas World War I fighting was tough, and barbaric, it was essentially a pissing contest and a modern day equivalency of wars that have been going for millennia over territory and backing your allies.

The Eastern Front was about wiping your enemy from the face of the earth. There was no room for both Nazism (along with their Fascist allies) and Bolshevik Communism to exist on this earth. The Germans of course committed the Holocaust, which they did not do in World War I. The Germans would wipe whole towns and villages off the map, just because they could... The Soviets for their part committed atrocities against the Germans and German civilians in the later part of the war - and were given the Green Light to do so by Stalin himself. World War I was a horrible war, a whole generation was butchered and damned (to quote the song "Green Fields of France"). A generation was lost in time. However, because of the aftermath of WWI, specifically the Versailles Treaty, a wound was left in Germany's national psyche, and it would fester - thus leading to World War II. But the Eastern Front was a completely different beast, on a far larger and more savage scale. The world had / has never seen that level of brutality and barbarism before or since.

There are so many great books you could read on the subject, so its hard to start. Are you looking for more of a general history, specific battles, biographies of generals, or personal stories? I can provide recommend readings for all... so just let me know.