International Gsei Web Opening Book Tournament

https://www.g-sei.org/igwobt/

Edition VII was in May 2018. I hope there is another.

.abk, .bin and .ctg books.

Most of the books are free (a few private or commercial).

There are links to download the books in the "Crosstable" and "Book rating" (from prior events also) tabs.
You may need to lick the "Update data" button first! (Some of the links are old.)

The "All games" tab has .pgn downloads for the latest event, and .pgn downloads for games per current and past participants.

--------
From SedatChess https://sites.google.com/site/computerschess/scct-book-cs-30-details
(Thanks to KameHameHaaaa for his 'SCCT Book XXX' thread this section.)

G-sei IGWOBT Editions I - VII: winners, table, .pgn's
https://www.g-sei.org/wp-content/IGWOBT/html/hof.html

The SedatChess SCCT Book CS XXX is in progress:
" ...
• Rather than tour...will be a rating (with min 400 games per player)
...
Polyglot (bin) books are played with best book move as disabled...
  E.g, Bin vs Bin  (BM ON) usually play 2 exactly same openings
  Just imagine, many games (each other) absolutely identical openings
... "
--------

The G-sei was in the old "bestmove" format, so only 2 games, white/black, per engine pair RR.