Copybooks don't get blotted very often these days, now that fountain pens and dip pens aren't used in schools, with the result that ink gets all over books, desks and people.
Instead, students use biros, starting a lot younger than they used to (that is, when they're not using classroom computers for special projects). But books still get grubby, and ink still stains. So how do you clean them? Copybook professional cleaning services? I haven't heard it yet...
Books are likely to get messy if they're read in conjunction with eating. Etiquette books will tell you not to read at the meal table at a formal meal, but there's nothing wrong with a good book to accompany a solo lunch. Or to help a reluctant young eater on the way. But food smears are inevitable, even with the most tidy eater.
To clean liquid mess from books: Sponge up the excess straight away, using whatever's handy. If possible, isolate the page with the mess so the water or other liquid only gets on the one page - grabbing the book by the spine and holding it so the water runs off the pages helps. If the liquid was sticky in any way, use a sponge damp with fresh water to remove the stickiness. Then dry the book flat, keeping it open on the page where the spill happened. This will stop the pages drying together and sticking, which can tear the pages when you try to open them next time. If pages stick together and water is the culprit, you can separate them with minimal damage by sliding a sharp knife between the pages.
To clear solid mess from book: Scrape off the excess tomato sauce, porridge or baby food (or whatever) with fingernails and a knife. Then proceed as before, cleaning off the excess with a sponge dampened in fresh water, followed by drying flat on the open page. Unfortunately, if the mess contained oil or grease of any type, the mark will be more or less permanent, leaving the paper somewhat see-through. However, don't despair and throw the book out. By the looks of some of my old diaries, many of which had candlewax falling on them and leaving a see-through mark, these grease marks on paper seem to fade with time, probably as the fats break down.
Ink can still get everywhere, even though ballpoint pens don't leak as much as the old fountain pens did. Small amounts of biro will just wash off hands, wooden desks and clothes with a bit of warm soapy water. Larger amounts need a bit of help in the form of strong alcohol (vodka, methylated spirits, surgical spirit, whisky...) applied to the spot. You may need to soak the ink stain with this to soften it before washing normally. Strong alcohol falling on ballpoint pen ink makes it go all marbly-looking as the alcohol dissolves the ink - this can be worth trying on paper for a special effect. To remove permanent pen stains from bags, clothes or carpet, strong alcohol is still your best friend. The sooner you get onto the stain, the better. Many people swear by hair spray as the best way to remove permanent pen stains - once again, it's the alcohol that does the job. Alcohol also works for removing filthy graffiti in permanent pen off plastic or vinyl, e.g. on school desks or playground equipment.