Ok, quite a lot happens in this post and some of it is dependent on other stuff, so send me a message if anything needs correcting.
Soul Reaver planned to telekinetically pull the book to him as soon as it was freed but it being grabbed by the chain ruined that idea. However, he mainly wanted it as it might have given him an edge in carrying out his main plan.
Soul Reaver's main plan is to teleport into the cocoon the moment he gets a glance inside.
The reliability of a teleportation spell hinges on a bunch of stuff, including how close the destination is (in this case, right in front of him) and how well he can visualize the space he's trying to enter (now that he's seen inside, quite well).
Certain focussed magical interference could also cause it to fail if not overcome, though Soul Reaver's a pretty good mage.
He WAS going to teleport in the moment an opening became visible in the chains, but since Abaddon did some talking after the hole closed I've made it that he does so afterwards.
Once inside, Soul Reaver wants to wrest the same spirit energy as Abaddon is using to try and counter him/keep him busy. Soul Reaver has soul absorbing powers too, and he'll be able to observe how Abaddon is doing it (without setting off the rune/sphere of annihilation) now.
As a secondary measure, he's also launching a surprise attack by thrusting Blooddrinker at Abaddon.
Let's see if any of the above works.