The best place to get started is the user manual. It provides a guide to the example programs and more.
In addition, Libtabula has a mechanism called Specialized SQL Structures (SSQLS), which allow you to create C++ structures that parallel the definition of the tables in your database schema. These let you manipulate the data in your database using native C++ data structures. Programs using this feature often include very little SQL code, because Libtabula can generate most of what you need automatically when using SSQLSes. There is a whole chapter in the user manual on how to use this feature of the library, plus a section in the user manual's tutorial chapter to introduce it. It's possible to use Libtabula effectively without using SSQLS, but it sure makes some things a lot easier.
The only two header files your program ever needs to include are libtabula.h, and optionally custom.h. (The latter implements the SSQLS mechanism.) All of the other files are used within the library only.
If you want to email someone to ask questions about this library, we greatly prefer that you send mail to the Libtabula mailing list, which you can subscribe to here: http://lists.mysql.com/plusplus
That mailing list is archived, so if you have questions, do a search to see if the question has been asked before.
You may find people's individual email addresses in various files within the Libtabula distribution. Please do not send mail to them unless you are sending something that is inherently personal. Questions that are about Libtabula usage may well be ignored if you send them to our personal email accounts. Those of us still active in Libtabula development monitor the mailing list, so you aren't getting any extra "coverage" by sending messages to those addresses in addition to the mailing list.
Libtabula is licensed under the GNU Lesser General Public License, which you should have received with the distribution package in a file called "LGPL" or "LICENSE". You can also view it here: http://www.gnu.org/licenses/lgpl.html or receive a copy by writing to Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.