Undecorate: The No Rules Approach to Interior Design by Christiane Lemieux, and Rumaan Alam.
This is a great book about how to decorate your space without making it look un-cozy. A lot of people think that when a place is designed it becomes unusable, or cold and uncomfortable. When really the goal is to make everything fit the client's needs and make the space fit the client. This book about 'un-decorating' shows us how to incorporate casual and cozy, but most importantly functional. Great inspiration, and a good book to lay on your coffee table when you are done with the space too!
Mid-Century Modern by Bradley Martin
Especially with "Mad Men" being such a trendy and popular show, mid-century modern style is all the rage. It is retro-chic, sleek, and fun. The clean lines, and pops of color can add to any space!
Lars Bolander: Interior Design and Inspiration by Lars Bolander
Lars Bolander is known for his eclectic style, use of interesting art pieces and pops of color. This book is a great showcase of some of his spaces and will provide great inspiration for any space.
Bookshelf by Alex Johnson
You will need a bookshelf to house all these books. This book is full of fun and creative ways to store your books. That said, this book is way too fund to be on a bookshelf, I think it is better displayed on a coffee table where many people can flip through it and see the unique shelving units. There are good ideas for kids rooms, or adult spaces too.
Last but not least,
Northwest Style: Interior Design and Architecture in the Pacific Northwest by Ann Wall Frank
Being from the Pacific Northwest, I couldn't leave this one out. Designs in the PNW often incorporate a mix of bringing the indoors out, and the outdoors in. Picturesque windows, and great outdoor living spaces (to use when it isn't raining).
Happy reading! I hope you find some good inspiration in these, or other design books! Design magazines are great places to seek inspiration as well! Let me know if you need any help finding inspiration, or solving a particularly tricky design problem, and...