Those Usborne books...

[happyhopefulmummy]

"that's not my robot. Its claws are too bumpy" or whatever.

Surely it should be "it's claws?" possessive it's? Like Sophie's claws?

It is spelt "its" in every book!

It's correct.

It's is "it is", which would be wrong in that context. :)

The possessive "its" has no apostrophe to distinguish it from "it's" as in "it is".

There are many other reasons to get annoyed by those books though (for example on the tenth reading in a morning).

Yes, I'm afraid it is correct.

Its, without an apostrophe, means "belonging to it",

eg The dog wagged its tail; or
Its claws are too bumpy.

It's, with an apostrophe, is a shortened form of "it is" or "it has", eg

eg It's the fourth day of July today (It is the fourth day of July today); or
It's got a bumpy tail (It has got a bumpy tail)

Ok I never knew this! So why then, can I write: "Sophie's claws" and also "sophie's going to the dentist" ? Or can I not?

It's only its where one has an apostrophe and one doesn't. So Sophie's claws and Sophie's going to the dentist are both fine.

Children do eventually stop demanding the "That's not my...." books by the way - have realised my 6 and 8 year olds haven't read them for quite a while now

Sophie's claw is possessive ie the claw belongs to Sophie - so the apostrophe is correct. BTW You wouldn't have an apostrophe if you write "its claw" because the word "its" is already possessive by definition.

"Sophie's going to the beach" is also correct, because here the apostrophe is used to show a missing letter ie what you are really saying is "Sophie IS going to the beach", but you are shortening it by merging two words together.

Apostrophes can be used to denote possession (example 1 above) or missing letters (example 2). Two quite different and distinct uses.

Ah so ok, I didn't know its already denoted possession...