Here are some of the new guidebook releases to inspire and help plan itineraries.

LONELY PLANET'S DISCOVER SERIES: Once the Lonely Planet reader was an adventurous young backpacker on a budget, ready to rough it and explore. But today Lonely Planet fans include older travelers who don't mind spending more for comfort and must-sees, not just offbeat adventures.

To cater to this audience, Lonely Planet has launched a new series called "Discover." The books are ideal for planning one- to two-week trips.

"Discover Europe" will be added to the series May 10.

The full-color books include maps, best-of lists, recommendations for a variety of budgets, tips from locals on visiting major attractions, and suggested itineraries organized by region, theme and length of trip. One especially nice touch: "If You Like" features direct readers to less well-known attractions by comparing them to better-known places. For example, the Venice section of the Italy guide says, "If you like the masterpieces of the Peggy Guggenheim Collection, we think you'll like these other modern art gems," and goes on to list Ca' Pesaro and Museo della Fondazione Querini Stampalia.

FROMMER'S DAY BY DAY GUIDES: Frommer's "Day by Day" city guides have been among the brand's best-selling books for years. Earlier this year, Frommer's launched full-size "Day by Day" guides to countries, states and other large regions. The full-color books are itinerary-based, include more than 100 maps and a pocket with a large pullout map, and are chock-full of photos.

"Frommer's Italy Day by Day," "Frommer's Ireland Day by Day" and "Frommer's Hawaii Day by Day" are available, while Costa Rica and Spain are due out in October.

The guides, all under $30, include easy-to-use features like what to see if you have a day, three days or a week, and "best-of" lists for lodging, dining and shopping. Also new from Frommer's is "500 Adrenaline Adventures," providing inspiration for anyone with a taste for unusual, wacky and heart-racing experiences. Among the ideas listed in the $20 paperback: ziplining, wildlife encounters, extreme eating contests, such as the famous Coney Island hot dog competition, and the annual Gloucestershire Cheese Rolling Race in England.

DK EYEWITNESS TRAVEL'S BACK ROADS: Road trips are a beloved way to explore America, but DK Eyewitness Travel has launched a new series this spring to inspire road trips in Europe. The "Back Roads" series includes guides to France, Italy, Great Britain, Ireland and Spain. Each $25 paperback describes two dozen "leisurely drives" designed to take anywhere from a day to a week.