Strong's is of course invaluable as a reference aid for those studying the Bible for any reason, and of great historical interest in and of itself, and a true bargain at this price.
However, I must say that a previous reviewers' recommendation of books by the Watch Tower Bible and Tract Society should come with a health warning. WTBTS is in fact the legal corporation otherwise known as Jehovah's Witnesses, an organisation who claim exclusive rights to interpret what they call "the truth", reject almost every mainstream Christian doctrine, and whose publications are, to say the least, exceptionally tendentious. Their translation of the Bible is notoriously poor in every sense, containing theological glosses masquerading as "translations", numerous errors and ommissions, and has been roundly condemned by virtually every respectable scholar, religious or otherwise, in the field, despite their claims to the contrary. Anyone reading their books should be aware of this.