The book industry is a cut-throat one, nowadays. In the UK Waterstones have a monopoly in the High Street and can therefore dictate trends in publishing. Meanwhile, mega internet businesses such as Amazon exercise enormous control over the pricing. In order to sell their books to these outlets publishers are obliged to offer huge discounts. And, of course, this means that the person who did all the hard work - the writer - gets an increasingly small share. 10% doesn't sound too bad if you are talking about £12, but 10% of £3 is not a living wage.
One way for an author to earn a little bit more from her book is buy acting as an agent. Kids in the Cockpit is available from various on-line stores, including Adlard Coles and Amazon. If you use these links to travel directly from this site to either one of these two retailers Jill will earn roughly 6% on anything and everything that you buy, including her books. The 6% is NOT added to your bill; you won't pay any more than usual.
Bearing in mind that Amazon get the book at a huge discount and sell it at a discount, the writer always earns more when you buy it directly from the publisher - but, by the same token, the customer generally pays less by buying from Amazon. The choice is yours...!