Here are the commands I use to install the requirements:

sudo apt-get install php-pear php5-xsl php5-mysqli mysql5-server php5-mysql php5-cgi apache2-mpm-worker libapache2-mod-fcgid
cd /usr/share/php
pear install MDB2 pear/MDB2#mysqli cache_lite 
mkdir /usr/share/pbooks/
cd /usr/share/pbooks/
cd /var/www/
ln -s /usr/share/pbooks/web pbooks

PBooks Code Installation

sudo mkdir /usr/share/pbooks
cd /usr/share/pbooks
sudo svn co http://www.pbooks.org/svn/pbooks/misc_projects/pbooks_portable/trunk/ .
sudo chmod 0777 /usr/share/pbooks/cache
sudo svn co http://www.nexista.org/svn/nexista/trunk/ ./nexista
cd apps
sudo svn co http://www.pbooks.org/svn/pbooks/misc_projects/pbooks/trunk/ ./pbooks
sudo svn co http://www.nexista.org/svn/nexista/apps/auth/ ./auth
cd /opt/lampp/htdocs
sudo ln -s /usr/share/pbooks/web/ pbooks

PBooks Database Installation

cd /usr/share/pbooks
cp config/my_db_admin_settings.php.dist config/my_db_admin_settings.php
vim config/my_db_admin_settings.php
php install_db.php
sudo cp config/config.xml.dist config/config.xml
vim config/config.xml
sudo cp apps/pbooks/config/config.xml.dist apps/pbooks/config/config.xml
vim apps/pbooks/config/config.xml