If I was in the position of your son, I would be interested in the Oxford Met CD and also the CRP 5 CD, if also if the english is a bit rusty also purchase the VFR and IFR communications CD's. Try one of the many pilots shops, ie pooleys.com or afeonline.com or transair.co.uk to name just a couple.
Also how about a interview books such as one of these:
Airline Pilot Interviews - Jasinski
This book concentrates on showing you how to prepare an impressive pilot employment package, and how to portray yourself in the most effective, professional manner during an interview.
Price: £26.50| £26.50 including VAT (Exempt)
Handbook of Pilot Selection - Hunter & Burke
This book describes the methods surrounding pilot selection, techniques largely applicable to any personnel.
Price: £65.00| £65.00 including VAT (Exempt)
Job Hunting for Pilots - Brown
This book has been written as a guide for Pilots trying to get a flying job.
Price: £14.95| £14.95 including VAT (Exempt)
or these will come in handy especially the multi engine book ...
Instrument Flight Procedures - Gjerlev
(Including RNAV and FMS operations) 57% of all accidents happen during descnet, approach, and landing, often as Controlled-Flight-into-Terrain (CFIT).
Price: £24.00| £24.00 including VAT (Exempt)
Multi-Engine Piston - Robson
This manual has been prepared for those pilots embarking on their first type endorsement on a Multi-Engined aircraft.
Price: £20.00| £20.00 including VAT (Exempt)
These books, are also good reference for any pilot:
Aerodynamics, Engines and Systems
This volume refreshes and expands the professional pilot’s knowledge of: • high-speed and heavy-jet aerodynamics; • gas turbine engines and their operation (both turbo-fans and turbo-props); • associated fuel control systems; • propellers; and • flight controls and other systems that make up the very complex but fascinating package that is the modern jet transport aeroplane.
Price: £25.00| £25.00 including VAT (Exempt)
Avionics and Flight Management Systems
This volume introduces the modern flight deck systems where the pilot’s primary role is one of systems management rather than manipulation of the flight controls.
Price: £25.00| £25.00 including VAT (Exempt)
Human Performance & Limitations
The most important information needed to perform the multi-functional tasks required by a modern jet is knowledge about the performance and limitations of its human crew.
Price: £25.00| £25.00 including VAT (Exempt)
Meteorology For Pilots Code: 8773E
Meteorology For Pilots - K. M. Wickson.
Giving a detailed weather prediction is a difficult task, and so is understanding the meteorological factors and their reactions. This is a comprehensive manual for all aeronautical students.
Transair Price £25.00
THIS BOOK ABOVE IS REALLY GOOD!
Some of the Microsoft flight simulator add ons are also a good thing to get:
A320 Pilot in Command Code: 3793D
Highly detailed airliner "A320 Pilot in Command". This is a complete airliner simulation using a 3D Active Panel, which gives you full room to move and a new dimension of realism in MS Flight Simulator!
Transair Price £24.99
Boeing 737 NG 600/700 Code: 3792D
Add on for Microsoft Flight Simulator 2002 & 2004. The B 737 NG is a highly realistic reproduction of Boeing`s New Generation Glass Cockpit Aircraft series.
Transair Price £24.99
I just touched the edge , there are many good books, and many good software packages that will help your son, and give him some good reference material for use his future career.