After clearing Runway 15R at IAH C172 pilot is instructed to use WP to WJ; hold short of 15L. Reporter taxis past WJ due to lack of signage and cluttered government airport diagram.

Narrative

The following may be an operational or logistical issue at IAH and involves two taxiway signs (or lack of). Upon landing at IAH on Runway 15R; I was directed to exit at the High Speed Taxiway WS. Local (Tower) control then directed me to proceed on WS and turn right on WP; left turn on WJ; Hold short of 15L. I read this clearance back to ATC and proceeded to comply with the clearance. My taxi diagram was available and being used.As I turned right on WP; I taxied past an unmarked taxiway on my left that was angled back approximately 135 degrees. I do not remember if there were any taxi lines curving off in that direction. IAH procedures are to NOT use reverse high-speed taxiways. I stopped taxiing to determine if this unmarked taxiway was WJ. ATC stated that I had passed my intersection and should now proceed to WL; turn left and hold short 15L. I read back this clearance and complied.I am familiar with this airport. The taxiway signs and markings are prominently displayed. The lack of a taxiway sign; coupled with the 'reverse' nature of the direction (and possible lack of lead-in taxi lines) makes this a potential area for similar events in the future.Furthermore; a review of the airport diagram is found to be lacking due to the small print necessary to depict such a large area. The letters; 'WJ' are superimposed over the runway making them appear to be 'WI'. Moreover; due to the limitations of the printable area; the information does not lend itself to rapid assimilation by the pilot (if you need to search for something on the chart; you are going to be 'heads down' in the cockpit).This problem could be resolved through any of the following:1. Install signs depicting the taxiway intersection;2. Not using a taxiway requiring a 135 degree turn;3. Painting a standard taxiway lead in line to the taxiway. Splitting the Airport Diagram into two separate drawings (possible North and South) allowing for larger diagrams and less clutter.