Unless you have a commentary on every book of the bible including Obadiah and Esther just for general life you need a commentary that covers the whole bible. They have their disadvantages and advantages because of their size but every Christian should have one. A good bible and the new bible commentary are the basics you need.
This is the best one-volume commentary by far (in the UK, at least, nobody even considers buying another), with an stunning list of evangelical contributors. Purposely concentrates on the flow of a text, which is always sensible, especially when space is so limited, as it inevitably is with just one volume. Most of the New Testament is verse by verse and in the OT bigger chunks are taken at once. The scholarship is very up to date and they rarely dodge difficult questions, although as would be expected they don't have enough space to be thorough. There is, however, so much information in this book that it is worth several times the list price. There are a few articles with titles such as: 'the Pentateuch', 'reading the letters', 'approaching the bible' etc. which are all very good, and all the books have introductions dealing with authorship, date, etc. The editors also recommend single commentaries for each book of varying difficulty which is very useful when you need to have a commentary with more detail than any one-volume can supply.
Please, for the sake of your spiritual growth, buy this book, and now not tomorrow.