If you are in the U.S., the United States Conference of Catholic Bishops sells the Catechism. I would think the edition they sell would be the most up to date. http://store.usccb.org/Catechism-s/2042. I have the one with the green cover and the compendium.
There are two editions of the Catechism in English. The first one came out in 1992, and the second came out in 1997. As the second one has been out for a lot longer than the first, there are far more copies in existence. I don’t believe you could get a 1st edition anywhere except perhaps a used bookstore.
The 1st edition isn’t necessarily “wrong”. Mostly the 2nd edition includes clarifications and additional footnotes, not corrections of heresy. Here are all the differences between the two:
Some versions of the 2nd edition do contain additional material, though. I like the green cover one because it includes a glossary and some additional indices that are quite helpful. Many of the pocket-size versions do not have that. The only pocket version that also includes all those extras is the one sold by the Pauline sisters in Australia. I picked one up several years back. I like it a lot. The pages are thinner (like Bible paper), but it is very portable.
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