I have enjoyed books for as long as I can remember and have several Maths books on my Kindle, a small number of which were free or very low cost. Now you don’t have to own a Kindle to read Kindle books as the Kindle app is free to download for any device you may own: PC, phone or tablet. It is possible to search Kindle books by price, so a search on Mathematics books by price from lowest to highest will give all the free entries; there are lots of toddler books and samples there but the odd useful book is available. A very useful search for low cost books is a search on popular Mathematics books, price low to high. which returns popular Mathematics and Science books for as little as 99p. .
Looking at the free offerings, these include Mind Hurdles: Mystery Number – a set of ‘number mysteries’, one or more of which would make a good lesson starter and Henry Ernest Dudeney’s – Amusements in Mathematics a puzzle collection (with solutions). The first set of puzzles will offer a trip down memory lane for those who remember money – pre-decimal! There are several categories of puzzles available. Or try Edwin Abbott’s Flatand the tale of a two-dimensional world occupied by geometric figures.
There are many other free Maths books online as you will discover with a little searching, see this collection for example.
Colin Foster’s KS3 Instant Maths Ideas (3 books) are now freely available online; these contain a wealth of ideas to try in the classroom. Colin Foster is an Assistant Professor at the Centre for Research in Mathematics Education in the School of Education at the University of Nottingham.
For GCSE try:
Complete GCSE Maths Revision text from CLCnet. Don’t be put off by the 2007 date – this is still useful. The text includes numerous set of questions for each topic by grade with solutions for all the examples.
AQA Further Maths text
‘Street Fighting Mathematics‘ by Sanjoy Mahajan, with the excellent sub-title ‘The Art of Educated Guessing and Opportunistic Problem Solving’ (note the link on the left to the free Creative Commons edition under Essential Info).
Thanks to Stephen Cavadino, I came across Nix the Tricks by Tina Cardone and many other contributors. This looks like an interesting read – discussing how the use of ‘tricks’ can lead to misconceptions.
STEM learning has an extensive library of free resources for Mathematics (and also for Computing, Design and Technology and Science) including textbooks; you can search the collection in various ways, a search for textbooks for ages 11-18 returns these results.
You will find a real treasure trove in this collection – see this separate page.
Any discussion on free Maths texts should include of course all the free texts available on the wonderful CIMT site (Centre for Innovation in Mathematics Teaching).
CK-12 provides an extensive range of open-source content and technology tools for students and teachers. See for example the algebra resources here; click on FlexBooks Textbooks to see the available books. Books such as CK-12 Algebra – second edition can be downloaded free in various formats, PDF, mobi and ePub. To download books you will need to sign in (free); you can create an account or sign in with Google, Facebook or Twitter.
You could even write your own! If publishing your own Kindle eBook feels a little too much right now – you could try something simpler!