We have been seeing that many books published with copyright notice like:

> Copyright © by xyz publication.<br> All rights reserved. No part of this publication may be reproduced, copied, or stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner.

Now I want to know:

-  How long this copyright last or sustain?
- How do I check if copyright is expired or not?
- Can books used as in public domain after expiration of copyright?

If a book doesn't have any copyright notice, then can it be used as in public domain?

Note: My concern is for  scanned versions of books.