Details on the text and its historical significance can be found on Google Books Eugene Odum: The father of modern ecology - UGA Today
The 1971 edition is currently out of print in many regions. Hodder & Stoughton published the UK version, while W.B. Saunders published the US version. Because copyright laws make reprinting expensive, the "PDF" has become the archival lifeboat.
1 1 Peer-reviewed chapter in press for an edited volume Scaling in ... - arXiv