Couple of questions here:
1. Is your dsl modem and wireless router in a separate location from your laptop, Debian box, and extra router?
2. Is your extra router a wireless router?
I am assuming that question number one is true and your internet connection and systems are in different locations. If your extra router is a wireless router you could make your second router a n access point and plug your Debian box and laptop into the router which would provide internet access to both. If your extra router is not a wireless router then you would want to bridge wlan0 to eth0 on your Debian box.
This is how it would work:
DSL MODEM -----> 188.8.131.52|Wireless Router|192.168.0.1---> 192.168.0.2|Wlan0
192.168.1.1|Eth0 (statically assigned)
Your dsl modem gives your wireless router a public IP address on the WAN side. Your router also has a privite IP address within your DHCP range, usually ending in '192.168.xxx.1'. Your Debian box picks up an address from your wireless router, lets say 192.168.0.2 and has a default gateway of 192.168.0.1. Now you can staticly assign an IP address to eth0 such as 192.168.1.1 and then give your extra router an ip address of 192.168.1.2 with a default gateway of 192.168.1.1 and you can setup its dhcp range for 192.168.1.3-254. So your laptop would get an IP address of 192.168.1.3 and a default gateway of 192.168.1.1. You need to bridge wlan0 and eth0 so that they become part of the same network.So basically and example from your laptop would be,
laptop sends request to internet so it first contacts 192.168.1.2 (extra router) which then contacts 192.168.1.1 (eth0) which then decides that it needs to send it onto 192.168.0.2 (wlan0) it then sends it to 192.168.0.1 (wireless router) which then sends it out via the dsl modem.
Here is a link for bridging networks http://linux-net.osdl.org/index.php/Bridge
Hope this helps!