Omar Khayyam was an 11th century poet, mathematician and philosopher, and the poems which appear in 'The Rubaiyat of Omar Khayyam' are attributed to him. The poems (or quatrains, to be more precise) were originally written in Persian, and the most popular translations into English were those by Edward Fitzgerald which date from the late 19th century.
'Omar Khayyam' was a popular book during the first half of the 20th century, and to acquire one during WW2 was obviously worth recording; it may well be that BB's mother found her edition in a second-hand bookshop, rather than buying it new.
I can't see any circumstance where one would buy a volume of poetry and simply record that the book was 'wiry'. That would be like buying a diamond ring, and merely recording details of the box it came in.
