A Garmin nuvi manual replacement is provided on the official Garmin website, as of 2015. The website offers manuals for many nuvi models, such as the nuvi 2599 LMT-D and the nuvi 66LM.
Visit Garmin.com and click Support in the menu located in the top right-hand side of the page. Then click Manuals under the I'm Looking for... heading, and click the Search for Manuals link. The Search Manual by Product Web page appears. Select Automotive from the next two drop-down boxes, and choose the appropriate year from the third drop-down box. Lastly, pick the appropriate nuvi model from the final drop-down list. Then click the Download link, and the manual opens in the browser.