Reporting this both to the Slimeknight/Mantle Team aswell as the TechReborn Devs;
TechReborn/TechReborn#630

Using;
Forge: 12.17.0.1954
Mantle: 1.9.4-0.10.1
TConstruct: 1.9.4-2.3.1
RebornCore: 1.9.4-2.5.1.36
TechReborn: 1.9.4-1.3.1.100

Crashlog:
http://paste.ee/p/Azwzq

Got this reported to me by one of our testers today.
Apparently the Lazurite Plate counts as a valid "modifier" type for Lapis (Luck) in the Tinker's Construct Book, which once hovering over the Lazurite Plate causes this Crash.

Not sure if it's a TC/Mantle side only issue but reporting it here so both sides know.

The Lazurite plate isn't rendered using a json file, it that could be the issue I can go into more detail. Just thought it may help for you to know that.

Seems to be on our side, as far as I see it's not connected to the Lazurite plate. Needs more investigation.

Well, but it has a model, right? Book items are rendered via the standard "render item into gui" code.

yeah it does, that wont be the issue then. Just wanted to let you know just in case.

Should be fixed by 4b42e30
It looks like your player died or got teleported while having the book open, and it didn't like it.