Unfortunately, pretty much all QBasic/QuickBasic books are out of print, but can still be found in used books stores - both online and in your community. Your search for books also benefits from the fact that QBasic is over 99% compatible with QuickBasic (lack of a compiler is the biggest difference), meaning that books written for either language are completely useful to QBasic programmers.

Recommended QBasic Books
Here are my suggestions on a few QBasic books to get you started. You'll probably have to buy them used because they are no longer in print. Most can be bought for about $10 each (that price includes shipping costs).

• QBasic by Example Perry
• Running MS-DOS QBasic Halvorson, Rygmyr
• MS-DOS QBasic: Microsoft Quick Reference Jamsa
• QBasic Made Easy Inman, Albrecht

I suggest Amazon.com as your first stop in looking to buy a book on QBasic.

Complete Listing
And here's a more complete listing of books. Browse through these to see if a title catches your attention. I generally do not include QuickBasic books because they tend to be several years older than QBasic books. QBasic 1.1 was released 5 years after the release of QuickBasic 4.5.

But since QBasic is a subset of QuickBasic, any books on QuickBasic you can get will be directly applicable to your QBasic needs.

• A Beginner's Guide to Qbasic Parker, Wertheimer, Meyer (1995)
• A Brief Course in Microsoft QBASIC Schneider (1991)
• A Brief Course in QBASIC with an Introduction to Visual Basic Schneider (1994)
• A Brief Introduction to Basic: Qbasic-Quick Basic Hochwald (1992)
• A Short Course in QBASIC Venit (1996)
• Absolute BEginner's Guide to Qbasic Perry (1993)
• Computers: Concepts and Applications for Users with Qbasic Nickerson (1993)
• Computers: Quick Look at Qbasic Tutorial Trainor (1995)
• Crash Course in Qbasic Perry, Potts (1994)
• Easy Programmign with Qbasic Toupin (1994)
• Fundamentals of Qbasic Programming: Problem Solving and Application Development Nickerson (1995)
• Illustrated Qbasic for MS-DOS 5.0 Venkateswaran (1992)
• Instructors Manual: A Brief Course in QBasic Schneider (1994)
• Introduction ot Programming with QuickBasic/QBASIC Meyer (1993)
• Introduction to Computer Programming with Qbasic Carney (1998)
• Introduction to Program Design with QBasic
• Introduction to Programming in QBasic Baumann (1993)
• Mastering Qbasic and QuickBasic Albrecht, Inman (1994)
• Microsoft Qbasic: An Introduction to Structured Programming Schneider (1991)
• MS-DOS Qbasic (Microsoft Quick Reference) Jamsa (1991)
• Power of ... Qbasic Goodwin (1991)
• Practical Qbasic Programming James
• Programmign Logic with QBASIC: A Workbook of Business Programming Applications Scott, Higgins (1993)
• Programming in QBASIC for Engineering Technology Craven (1998)
• Programming Q-BASIC for Engineering Technology Craven (1998)
• Programming With Qbasic: Be an Expert! Scherpenisse (1995)
• QBASIC - A Step by Step Reference Lee (2004)
• Qbasic (Microsoft) Bent, Sethares (1996)
• QBASIC A. to Z. Reference Sinclair (1993)
• QBASIC Beginners Book Sinclair (1993)
• Qbasic by Example Perry (1993, Que)
• Qbasic for Beginners Tornsdorf (1993)
• Qbasic for Beginners Tornsdorf, Tornsdorf (1992)
• Qbasic for Business Problems Solving Forsmark (1995)
• QBASIC for Rookies (1993)
• Qbasic for Students Trombetta (1993)
• QBASIC Fundamental and Style Shelly, Cashman (1993)
• QBasic Fundamentals and STyle with an Introduction to MS Visual Basic Quasney, Maniotes, Forman (2000)
• QBASIC Fundamentals and Style Quasney, Maniotes (1993)
• Qbasic Games and More! Sexton (1993)
• QBasic Games and More Sexton (1996)
• Qbasic Made Easy Inman, Albrecht (1991)
• QBasic Program Development Jones (1996)
• Qbasic Programming 101 Perry (1993)
• Qbasic Programming for Dummies Hergert (1994)
• Qbasic Programming: Structured Applications Nickerson (1993)
• Qbasic Programming Schneider (1991)
• QBASIC Text & Working Model CD Shelly, Cashman, Gleason (1997)
• QBasic Using Subprograms, 2nd Ed. Quasney, Maniotes, Formen (1997)
• QBASIC with an Introduction to Visual Basic for Engineering, Mathematics, and the Sciences Schneider (1994)
• Qbasic: A Brief Introduction Wennington (1996)
• Qbasic: A Short Course in Structure Programming Martin (1998)
• Qbasic: An Introduction to Programming Shelly, Cashman, Gleason (1996)
• Qbasic: Beginning to Advanced Hochwald, Dachslager, Yuhnke (1994)
• QBasic: Includes Microsoft QBasic Interpreter Baumann (1992)
• QBasic: Programmer's Quick Reference by Kris Jamsa (1991).
• Qbasic: The Language of MS-DOS James (1994)
• Qbasic Amoroso, Boyd, Cohen (1994)
• Qbasic Baumann, Baumann, Mandell (1996)
• Qbasic Cassel (1994)
• Qbasic Fenton (1998)
• QBASIC James (1992)
• QBasics by Example (1993)
• Qbasic for Students Trombetta (1993)
• Quick BASIC Programming for Scientists and Engineers Noggle (1993)
• Quickbasic & Qbasic Dejesus (1993)
• Quickbasic and Qbasic Using Modular Structure Bradley (1993)
• Running MS-DOS: Qbasic Halverson, Rygmyr (1991)
• SELECT: QBasic Fenton (1993)
• Structured PRogramming with Microsoft Qbasic Goldstein (1993)
• Structured Programming with Microsoft Qbasic Goldstein (1993)
• Structured QBasdic Lawlor (1996)
• Teach Yourself Qbasic in 21 Days Shammas (1993)
• Teach Yourself Qbasic Butkus (1994)
• The Beginner's Guide to Qbasic Melnikova, Bonushkina, Krylov (1994)
• The Complete Idiot's Guide to Qbasic Perry (1994)
• The Waite Group's Qbasic Primer Plus Mackenroth (1991)
• The Waite Group's QBasic Reference Plus by Waite, Prata, et al. (1991, Que)
• Understanding and Using Qbasic Barron (1994)
• Using Qbasic Feldman, Rugg (1991)
• Utter Novice Guide to Q-BASIC Aitken (1996)
• Van Wolverton's Guide to Qbasic Wolverton (1992)

I'm not aware of any online source for the content of these books. In other languages, full text of books are sometimes available.