Somewhere around book four or five, I stopped copying my own previous copyright page and actually looked into what belongs on it, and why. Most of the advice I found online — Kindlepreneur's guide is a genuinely good one — is written for US self-publishers and references the US Copyright Office, Bowker ISBNs, and Library of Congress conventions without much acknowledgement that the rest of the English-language publishing world does some of this differently. As a UK author distributing wide, I had to piece the UK side together myself. Here's the short version of both.
What both sides share. A copyright notice — the © symbol, the year, and your name or pen name — followed by an "all rights reserved" statement restricting reproduction without permission. A fiction disclaimer, along the lines of: this is a work of fiction, and any resemblance to actual persons, living or dead, or actual events, is purely coincidental. Your ISBN, if you're distributing beyond a single platform's free identifier. An edition statement, if you've substantially revised a book after its first release. All of that travels fine across the Atlantic unchanged.
Where the US differs. US self-published books commonly reference the ISBN issuer, Bowker, and — for print books seeking library placement — a Library of Congress Control Number, which has to be applied for before publication and isn't something most indie authors bother with unless they're specifically targeting library sales. The rights language typically sits under general US copyright law without needing a specific statutory citation.
Where the UK differs. British and Commonwealth copyright pages include a line most American authors have never seen: "The right of [Author Name] to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988." This is a moral rights assertion — the right to be credited as the author — which UK law treats as a separate, assertable right rather than something automatically bundled into copyright ownership the way US law broadly does for most literary works. Traditionally-published UK books also often carry a line noting that a Cataloguing-in-Publication record is available from the British Library, the UK equivalent of the Library of Congress reference — again, more relevant to print runs seeking library placement than to a typical wide-distributed ebook.
A working template. For a UK-based indie author distributing wide — which is exactly my own situation, selling direct and through Books2Read into both markets — I use something close to this: the copyright notice and year; "All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means without the prior written permission of the author"; the moral rights assertion under the 1988 Act; the fiction disclaimer; and a line crediting the cover designer where relevant. It covers the UK requirement properly while reading naturally to a reader anywhere else.
None of this is legal advice — I'm a novelist, not a solicitor or an attorney, and if a book touches genuinely sensitive territory (real events, real people, professional or medical content) that's worth an actual conversation with someone qualified. But for the ordinary indie novel, getting this page right once means never having to think about it again.