Yarn bombing : the art of crochet and knit graffiti / Mandy Moore and Leanne Prain. (OCLC #305104129)
RDA 3.5.1.4.14 on recording the Dimensions of volumes says to record only the height of the volume (in cm or mm as appropriate), unless the width of the volume is either less than half the height or greater than the height, in which case both are recorded. For this volume, that would be:
21 x 23 cm
and in the MARC:
300 __ ǂa 231 pages : ǂb color illustrations ; ǂc 21 x 23 cm