SQL 2012 :: Finding Lock Escalation Cause

While running SQL Server Profiler I reached some Lock:Escalations. When I searched for Statements having same SPID as Lock:Escalation event I realized that one of delete statements causes this. Is there any way to find out why lock escalation in such place occurres?

Statement is like:

delete from BOOK_IN_LIBRARY where libraryId in (,,,,); <-20 elements ids

CREATE TABLE BOOK_IN_LIBRARY(
[libraryId] [bigint] NOT NULL,
[bookId] [bigint] NULL,
[otherData] [bigint]NULL,
[otherData2] [int] NULL,

[Code] ....