Just a word of caution, but SIGHT-reading skills don't improve so well when you are playing tunes that you already KNOW. There are plenty of sight reading exercise books at your local music store (the one that caters the most to piano teachers is a good bet), and some good software. Sight reading from a fake book is a definite skill in itself, a highly useful one, too, but if you are determined to work on sight reading, at least picking tunes you DON'T know (even slightly), recording the effort, then listening back and comparing to the chart will speed up this skill.
Fake books are more a way of jogging your memory on tunes you know than a proper sight reading primer...
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An arranger is just a tool. What matters is what you build with it..!