I don't know of any particular books on mailmerge, though the Mailmerge Tip & Tricks 'Sticky' thread at the top of this forum (https://www.msofficeforums.com/mail-...ps-tricks.html) addresses a lot of common issues.

As indicated in my previous reply, though, your problems have less to do with mailmerge and more to do with proper document formatting. Your problems were indicative of a document in which someone had overridden the Style definition for the paragraph in which the filed was located to make it look different than what the Style definition says. This is quite common and afflicts the documents created by many people who haven't taken the time to learn to use Word properly. The solution is to learn to use Styles the way they are meant to be used.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]