Please help me select few books in Science, History, Geography and RS for extra reading. DS needs extra material as he has already covered the topics and now bored.

Talk to the teachers first ... how has he covered the subjects? If they are following the NC then there is a set content.

What age? Take him to the local library and let him choose some books that appeal, fiction and non-fiction.

+1
How has he already covered the topics?
It's not a good idea to work ahead in the national curriculum as they do then get bored in class even if they haven't actually covered the work as required.
If he is bored in all these lessons it sounds like there is something going in that isn't going to be dealt with by more work outside of school.
If he is finding the school work restrictive then it's great to widen his horizons but he should choose something that interests him in particular and research it for himself, not just from books or the internet but in practical ways - visits, investigations, experiments etc depending on what it is.
Teachers will often be happy to suggest reading that's relevent to class work but takes the motivated students into broader areas or encourages deeper thinking.
I would focus on broadening horizons rather than getting ahead.

My Dd also felt that she had covered various topics in both years 7 and 8 at secondary school because her primary school was particularly good and especially the top table children were given a lot of extra work. She has now learnt that there is often more depth to the topics and that re-doing them can be really beneficial. I would ask the teacher to give your DC extension work in class once he has covered to work set for everyone. It is really important to do the work set for the rest of the class because you may find your son is missing bits. This was certainly the case with my daughter. She was ahead as in knowing a lot of the curriculum from years ahead in science but glaring gaps were found in her understanding of some of the basics.

Looking at OPs posts, she is only waiting for indie school results - of which the teachers have assured her her son will get the fiercely competitive one...and one is Westminster Upper.

If her son is coming from private primary, perhaps he has covered their curriculum, as they are not necessarily bound by the national curriculum as we know it, but certainly won't have done it in enough depth. How often, after all, do we hear of parents who think their child is the top of the top table yet still they fail to gain a place through the 11+?

To the OP, let your child read around subjects, read novels that interest him, learn a new skill (like cooking, rock climbing or a sport). Doing something "beyond school" does not have to be academic but can be so much more worthwhile. You and he could volunteer together at an animal shelter, soup kitchen or somewhere. He could do a paper round.... help expand his knowledge and interest in different ways.

Great suggestions - he is already a great climber and keen on cricket. I just signed him up for First Aid volunteer. Thank you!

On the Origin of Species
The Selfish Gene
A Brief History of Time
The Decline and Fall of the Roman Empire
The Times Atlas of the World
The Bible
The Quran

Those should keep him occupied for a bit.

Slightly tongue in cheek there perhaps...

Try sourcing some interesting biographies: eg Surely You’re Joking, Mr Feynmann (an inspiring US physicist but a lot more accessible than Mr Hawking!)

Try some off the wall primers: eg “this is not a Maths Book” -buy via Amazon. Thrre’s a whole series if you like them.

Look at A Capella Science and asap Science channels on Youtube , and some of the TED talks.

Get him a teach-yourself-origami book and some origami paper

Good Housekeeping Step By Step is a nicely illustrated hardback cooking book that explains very well and covers a wide range of cooking skills

And get him a bulk pack of stamps, a stamp album, and a copy of Gibbon’s Stamp Collecting primer. There’s a lot of geography and history in philately.

Yes it was slightly tongue in cheek I admit, although to be fair the OP's question was very open and vague and she didn't specify what age her DS was. (he could have been 6th form for all we know).

And to be completely honest I do sometimes find these "my child is so bright and advanced he/she gets bored at school, please help" posts slightly tiresome...