Just added to the CMRLS Professional Collection: Easy MARC, 5th edition, by Scott Piepenburg.
ISBN: 978-1-933170-31-2; CMRLS Classification Number: RCO 025.3 Piepenburg.
Lots of explanations and examples and much more readable than the documentation from Library of Congress or OCLC. Integration of cataloging rules and ISBD punctuation.
I'll have the book with me on Wednesday, July 9, when I teach a workshop on reading a MARC record at the Thayer Memorial Library in Lancaster. There's still time to register if you want to join us.