Here are some possibilities (see below). It's possible to email bibliographic search results from Wordcat FirstSearch, too if you wanted them.
There are at least 133 books from the time period that could fit the bill, but finding the item seems to depend on the cataloging of the contents too in this case. With a visual description being the primary bit of information, seeing covers would be useful too. You might try to interlibrary loan the most promising candidates when Covid goes away some, and borrowing services at your library start again.
Might be this (cover would be different)
https://www.amazon.com/Mysteries-of...&keywords=9780860204923&qid=1614870725&sr=8-1
Mysteries of the unknown.
Author(s): Miller, Carey.
Maynard, Christopher.
Wilding-White, Ted.
Publication: London : Usborne,
Year: 1977
Description: 96 pages : color illustrations ; 28 cm
Language: English
Contents: pt. 1. Monsters -- pt. 2. Ghosts -- pt. 3. UFO's.
Standard No: ISBN: 0860204928; 9780860204923
SUBJECT(S)
Descriptor: Monsters.
Ghosts.
Unidentified flying objects.
Ghosts.
Monsters.
Unidentified flying objects.
Note(s): Cover title./ Includes index./ The material in this book was also published as three books, All about Monsters, All about Ghosts and All about UFO's in Usborne Publishing's World
of the Unknown series.
Class Descriptors: Dewey: 001.
Or this:
Here is pic of it:
Title:
All about UFO's /
Author(s): Wilding-White, Ted.
Publication: London : Usborne Pub. ; Tulsa, Okla. : Published in the USA by EDC Pub.,
Year: 1977
Description: 32 pages : chiefly color illustrations ; 28 cm.
Language: English
Series: The World of the unknown; Variation: World of the unknown.; The World of the unknown.
Standard No: ISBN: 0860201503; 9780860201502
Abstract: Investigates in text and illustrations the mystery of UFO's and suggests some possible solutions.
SUBJECT(S)
Descriptor: Unidentified flying objects -- Juvenile literature.
Unidentified flying objects.
Unidentified flying objects.
Genre/Form: Juvenile works.
Children's nonfiction.
Note(s): Includes bibliographical references (page 32) and index.
Class Descriptors: LC: TL789; Dewey: 001.9
Responsibility: [written by Ted Wilding-White].
Material Type: Juvenile (no specific ages) (jau)
Document Type: Book
Entry: 19841126
Another:
Mysterious visitors :
the UFO story /
Author(s): Le Poer Trench, Brinsley, Lord Clancarty, 1911-1995.
Publication: London : Pan Books,
Edition: Rev. ed.
Year: 1975
Description: xiv, 175 pages, 16 unnumbered pages of plates : illustrations ; 18 cm
Language: English
Standard No: ISBN: 0330242520; 9780330242523 LCCN: 75-323620
SUBJECT(S)
Descriptor: Unidentified flying objects.
Unidentified flying objects.
Note(s): Originally published in 1973 under title: The eternal subject./ Includes bibliographical references and index.
Class Descriptors: LC: TL789; Dewey: 001.9/42
Responsibility: Brinsley Le Poer Trench.
Document Type: Book
Entry: 19750908
Update: 20190122
Accession No: OCLC: 1676843
Provider: OCLC
Database: WorldCat