The
pdf file
holds the final manuscript of my forthcoming
book "Proof complexity" prepared for the CUP.

It differs at places significantly from the earlier drafts
(Dec.'17 and Feb.'18) that were available here. In particular,
there is one more section in Chpt.21 (on The proof search problem)
and one more chapter (on The nature of proof complexity).
The eventual printed book will differ from the manuscript
by corrections (check their
list) done during the copy-editing
process (also page numbers will appear in the Index at the very end).

J.K., 20.May 2018