Tamas Hazslinszky (2003?):
Show Caves of Hungary,
Published by Delta Publisher of Trade Papers.
This is a 6 page leaflet 20 x 20 cm.
Kessler Hubert (1957):
Az örök éjszaka világában,
László Jakucs (1961):
Gefangen in der Baradla-Höhle,
Forschungen in den unterirdischen Labyrinthen Ungarns
Leipzig Brockhaus 1961.
This book about caving in Hungary, especially in the Baradla cave near Aggtelek, is actually in German!
It was published in GDR during the cold war, when east Germany belonged to the Warshaw Pact.
Obviously there is also a Hungarian version, but no English version AFAIK.
Janós Haas (2013):
Geology of Hungary,
Regional Geology Reviews book series (RGR), Springer 2013, ISBN: 978-3-642-21910-8.