Inconsistencies in the command summary in User Guide

[nus-se-bot]

Describe the bug
The command summary in the User Guide has some inconsistencies with the rest of the User Guide. In particular, listBook command's [a/Author] should be [a/AUTHOR] since AUTHOR is a parameter supplied by the user, as stated in the User Guide's command format section. Also, addReview command does not follow the same format as the one stated in section 3.2.1.

To Reproduce
Steps to reproduce the behavior:

1. Go to the User Guide
2. Scroll down to '5. Command Summary'
3. See the errors

Expected behavior
Should be consistent with the rest of the User Guide to avoid confusion.

Screenshots

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Reported by: @whyjayxp
Severity: Low

_{[original: nus-cs2103-AY1819S2/pe-dry-run#844]}