Hobbes's LEVIATHAN is not only the most important work of political philosophy ever written in English, it is the work - even more than the writings of Francis Bacon - that kicked off the English tradition in philosophy. Many other claims are made for it, some praiseworthy, some negative. Its materialism caused countless authors to condemn its atheism, while its cold equations reduced man to his "price", in the eyes of many kicking off the tradition that ended with von Mises, Hayek, and Gary Becker (whether fair or not). He is also one of the earliest major figures in the social contract and natural law traditions. On almost every level it remains one of the most original and important books in the history of philosophy, and might be, even today, the most important philosophical book ever written in English, whether you agree with a word he writes.
The problem with Amazon is that it often clumps editions under a single roof. And editorial comments might have nothing to do with the version one is about to purchase. I own five editions of Hobbes's masterpiece, yet I don't own the best edition, the one edited by Noel Malcolm and which is referred to in the editorial reviews section: Thomas Hobbes: Leviathan (Clarendon Edition of the Works of Thomas Hobbes). I would love to own this, but I simply don't have $300 to drop on a book, even in three volumes. But if Malcolm's intro is anything up to the level of what he did with Hobbes's CORRESPONDENCE, it qualifies as something that any serious student of Hobbes should read.
The five editions I own are the ones edited by Curley (Hackett), Tuck (Cambridge), Macpherson (Penguin), Shapiro (Yale), and Martinich (Broadview). Until Oxford graces us with a paperback edition of the Malcolm, I would recommend these five in this order: Curley or Tuck, Martinich, Shapiro, and Macpherson.
There is little reason to prefer Leviathan: With Selected Variants from the Latin Edition of 1668 to Hobbes: Leviathan: Revised student edition (Cambridge Texts in the History of Political Thought), or vice versa. Both have outstanding introductions, both contain variants of the text, and both have excellent commentary and bibliographies. I generally find I prefer the Cambridge to the Hackett simply because it has a better binding. But you can really toss a coin and do as well with one edition as the other. A. P. Martinch has been as active as any Hobbes scholar as there is today, having written two introductions to his thought, a Hobbes dictionary, a book on Hobbes's religious beliefs, and the best recent biography on Hobbes. His edition of LEVIATHAN, Leviathan, revised edition (Broadview Editions), is an outstanding one. WARNING: Broadview also publishes an abridged edition of LEVIATHAN, so take care to buy the correct edition. I'm not much of a fan of the Shapiro edition that was produced in the overall outstanding Rethinking the Western Tradition series published by Yale University Press. The weakness of that series is that the press rarely expends much effort in providing an improved or definitive text of any of the works in the series. The press relies on public domain texts. In this case the text is largely just the 1651 text with modernized spelling, unlike, say, the Hackett edition produced by Curley, which included variants in the later Latin translation that Hobbes himself made. The value of the Yale edition lies in the four original essays appended to the text. I find that the essays are often worth the cost of the book even if the version of the text is rather pedestrian, such as their edition of Descartes.
I do not recommend the Penguin edition edited by C. B. Macpherson. I do, however, recommend purchasing a rather cheap used edition of the Penguin edition simply in order to get the introduction by Macpherson. One of the great members of the political Left of the previous generation, Macpherson was the author of a profoundly important book entitled THE THEORY OF POSSESSIVE INDIVIDUALISM: FROM HOBBES TO LOCKE. While some of his specific historical claims about possessive individualism cannot be supported by close readings of the philosophers in question, there still is no question that he has identified and trenchantly critiqued undeniable trends in the liberal tradition (using "liberal" in the more precise sense of those who are defenders of property rights and a free market, so that Ronald Reagan is quite properly considered a classic liberal). While Macpherson is not always correct in what he says of Locke and Hobbes, his essays are always worth reading and of the greatest interest. Likewise, moving to the far Right of the political spectrum, the older edition of LEVIATHAN featuring the famous intro by Michael Oakeshott cannot be recommended at all. Oakeshott's introduction, however, remains essential reading. Four essays on Hobbes have been collected in Hobbes on Civil Association, but the better way to acquire both the famous intro and Oakeshott's other famous essay on Hobbes, along with the best of the rest of his essays, is by purchasing his Rationalism in Politics and other essays.
I hope this helps prospective purchasers of Hobbes's great work of political philosophy. Even though I am politically far to the left of Hobbes, I find nearly every page of his work to be fascinating. I virtually never agree with Hobbes, but I never find him boring. Some on the Right do not want to claim Hobbes as a conservative, based on his atheism and his belief in an all powerful central government (or leviathan) to keep people from destroying one another, but his central assumptions - that people are driven by self-interest, that something like a market dominates society, that sympathy and compassion should not be motives for behavior - are shared by today's Right. There is a way, however, of analyzing both Hobbes and almost all other prominent political thinkers, and that is by asking: "Who do you trust?" Hobbes is unusual for a conservative in trusting government self-interested, self-seeking individuals. One could ask the same question of Locke, Rousseau, Marx, Bentham, Rawls, de Maistre, Mill, Jefferson, Lincoln, Nozick, and so on, asking what force in society they most trusted to foment to public good. Most conservatives today tend to trust the unregulated free market and to distrust government. I tend to distrust government, but even distrust the market (which I don't believe either is or ever could be truly free) even more. Rousseau also distrusted government, but distrusted the market even less, while Jefferson distrusted government, but saw the market as a source of evil. Lincoln, on the other hand, both trusted, to a degree, the market and central government, and in fact saw the two working hand in hand (Lincoln at his most typical was the government building a transcontinental railroad by handing out contracts to private corporations). As far as I know, no one has attempted a history of political thought in this vein, but I think it would produce some fascinating results. But regardless of how one reads political history, Hobbes will remain one of the 3 or 4 most important figures with whom to come to terms.