It could work, then again it could backfire on you. The guy probably said this in order for writers to stand out from other writers. Did he say to send the 50 pages in a "bright red" envelope? That's the other way to get noticed. It's up to you. I'd try the query letter and pitch first. Find an editor (there are some in writers groups) to help you write the query letter. Maybe you could a good writing book that gives examples of query letters. Good luck!

I would stick with query letters - if your letters are getting tossed, it's because they are not well written, not because the editor isn't interested in a guide book (after all, you're only sending query letters to those editors and publications that you've already researched and determined are a good fit for your guidebook, right? )

A good well-written query letter specifically for a guide book you'd like published should definitely include some short teasers of the content, for example:

"In my section on cuisine, I dined at the top 3 restaurants as ranked by the Michelin Guide as well as the top 3 restaurants recommended by locals, compared them all on food quality, service, and cost, and asked other patrons at all six restaurants to recommend a favorite entree."

You could, if you like, include a short sample chapter to give an editor a good feel for your particular voice and style of writing. But I think 50 pages is extremely excessive.

And for the record, I do believe that query letters - whether or not you include a brief sample of your writing - should be sent snail mail UNLESS the publication indicates a preference for email.