Forgive me Father, for I have sinned. Only with a pencil, but still, I’m incurable. Every book I read, I scribble in the margins. With library books I do it lightly and always erase after the event – promise. With books I own, the doodles lie wantonly in my wake, enigmas for the next poor sap to navigate.

As a writer-cum-reader, I’m prone to underlining key quotes, plot points, grace notes: all the things I admire and envy about the story in hand. As a chronic word nerd, I circle terms and phrases I’ve never met before, like nef (a model ship), or chatoyant (shifting in lustre). And as a crossword maker, I single out words with great clue potential. Like the day I realised turpentine holds two synonyms – enter and input – or that ogle is ‘go’ short of Google. Later, once the finale is done and dusted, I’ll go back through the book and jot down all these discoveries into my crossword book of spells.

With clue-making in my sights, every doodle is a kind of shorthand. Zigzags mean anagrams, like taipan/piñata/patina. DM is Double Meaning, such as moulder: the maker, and to decay. Slashes demonstrate how certain words can be broken into pieces, like harpo/on or outre/aching. A backward arrow reveals a word’s treasures in reverse, such as pampas revealing two rhymes – sap and map – when spun. Does the habit block my pleasure as a reader? Sometimes. Does it hinder my growth as a writer? Only when I let it. But the internal struggle can be ferocious.

As a teen, before puzzling became a job, I suffered the same fetish, converting Updike and Nabokov into a graphite blizzard, ransacking each novel for quotes and fertile words, or stuff that needed checking in the dictionary. Earthly Powers by Anthony Burgess holds the record for deepest vocab. Back in 1985 the book introduced me to sixty-plus words I’d never seen before, from aspergillum (holy-water sprinkler) to skirl (a bagpipe blast). Günter Grass taught me glabrous (hairless); and Margaret Drabble, syllabub (cream dessert).

Nowadays I still scribble in the margins, gathering clue ammo as I read, or juicy passages to savour down the track. Mind you, after so many years of word-harvesting, the vocab frenzy has eased a tad, though a recent exception was The Road by Cormac McCarthy. A sublime book, it almost felt written in LOTE. In the space of one yarn I learnt that gryke is cleft limestone, gambrel is a gabled roof, firedrake a dragon, and pampooties are deerskin moccasins. And that’s just a fraction of the exotica.

That’s why books are rich. More than stories, they are jungles rife with letters and ideas – both the writerly and crossword kind. At least that’s my defence, HB in hand. Of course, if you want to avenge every violated author of the last thirty years, then download this post and scribble on the copy for dear life. Go on, I dare you. Zigzag and squiggle. Slash and loop. Darken the hollow of every o, underline the odd bits and turn my name into Devil Sadat or dead vitals. I deserve no better.

David Astle – alias DA on the puzzle page, and the dictionary guy on SBS’s Letters and Numbers – is the author of Puzzled: Secrets & Clues from a Life Lost in Words. See more of his verbal mania at davidastle.com, or come hear him launch the Writers Victoria’s 2012 programme at the Wheeler Centre this Friday, 9 December at 6pm.